NWCG Glossary of Wildland Fire, PMS 205

This glossary provides the wildland fire community a single source for wildland fire and incident management terminology commonly used by the NWCG and its subgroups.

Glossary entries related to Organizations, IT Applications, and NWCG Positions have been removed from the glossary based on term inclusion criteria. For more information about the glossary and the criteria, see the About the NWCG Glossary page or the NWCG User Guide for the Glossary of Wildland Fire, PMS 937.

Reference Definitions

Some of the terms within this glossary will be followed by initials or will have references or comments at the end of the definition to help broaden the recognition and understanding of the term. An explanation of those references is as follows:

Also called: Means there is another term that may sometimes be in use, but is not defined in this glossary.
Acronym: An abbreviation formed from the initial letters of other words and pronounced as a word. An acronym appears in parentheses following the term.
Initialism: An abbreviation consisting of initial letters pronounced separately. An initialism appears in parentheses following the term.
See: Means there is another, preferred term that should be used instead. In such a case only the preferred term is defined in this glossary.
See Also: Means there are one or more related terms that may also be of interest to the glossary user. The related terms are also defined in this glossary.
Synonym: Means the term is synonymous with another. The terms have the same, or essentially the same, definition and the terms are interchangeable in their use.
Definition Extension: An example, further explanation, or usage guidance in support of the definition.

Glossary Acronyms/Initialisms

6 (1) | A (126) | B (94) | C (160) | D (102) | E (67) | F (261) | G (48) | H (90) | I (83) | J (10) | K (4) | L (74) | M (92) | N (31) | O (47) | P (133) | Q (6) | R (100) | S (221) | T (71) | U (28) | V (37) | W (60) | Z (1)
Macroscale Fire Pattern Indicator
  • Large single fire pattern indicator or overall patterns of indicators that are readily visible from a distance. 
Main Ridge
  • Prominent ridgeline separating river or creek drainages. Usually has numerous smaller ridges (spur) extending outward from both sides. 
Major Disaster
  • Any natural catastrophe or, regardless of cause, any fire, flood, or explosion, in any part of the United States, which in the determination of the President causes damage of sufficient severity and magnitude to warrant major disaster assistance. 
Major Repair (Aviation)
  • A repair (1) that, if improperly done, might appreciably affect weight, balance, structural strength, or other qualities affecting airworthiness or (2) that is not done according to accepted practices or cannot be done by elementary operations. 
Male Coupling
  • An externally threaded hose nipple which fits in the thread of a female (internally threaded) swivel coupling of the same pitch and diameter. Nozzles attach to this type of coupling. 
Management Action Points
  • Geographic points on the ground or specific points in time where an escalation or alternative of management actions is warranted. These points are defined and the management actions to be taken are clearly described in an approved Prescribed Fire Plan. Timely implementation of the actions when the fire reaches the action point is generally critical to successful accomplishment of the objectives. Also called Trigger Points. 
Management by Objectives
  • In ICS, this is a top-down management activity which involves a three-step process to achieve the incident goal. The steps are: establishing the incident objectives, selection of appropriate strategy(s) to achieve the objectives; and the tactical direction associated with the selected strategy. Tactical direction includes: selection of tactics, selection of resources, resource assignments and performance monitoring. 
Management Requirements
  • The technical and scientific specifications for management activities or potential actions mandated by the agency administrator and defined in land/resource management plans. Management requirements are derived from land/resource management plan and fire management plan standards and guidelines information. 
  • Individuals within ICS organizational units that are assigned specific managerial responsibilities, e.g., staging area manager or camp manager. 
Manual Weather Station
  • A non-telemetered weather station that provides one observation every 24 hours for manual entry into WIMS. 
Manually Regulated
  • A proportioning method or device that requires a manual adjustment to maintain a desired mix ratio over a changing range of water flows and pressures. 
Marine Air
  • Air which has a high moisture content and the temperature characteristics of an ocean surface due to extensive exposure to that surface. An intrusion of marine air will moderate fire conditions. Absence of marine air in coastal areas may lead to more severe fire danger. 
Marine Climate
Maritime Air
Mass Arsonist
  • An offender who sets three or more fires at the same location during a limited period of time. 
Mass Fire
  • A fire resulting from many simultaneous ignitions that generates a high level of energy output. 
Master Fire Chronology
  • Chronological listing of the dates of fires documented in a designated area, the dates being corrected by crossdating. Size of the area must be specified. Also called composite fire interval. 
Material First Ignited
Mathematical Model
  • A model that is a quantitative and mathematical representation or simulation which attempts to describe the characteristics or relationship of physical events. 
  • Hand tool with a narrow hoeing surface at one end of the blade and a pick or cutting blade at the other end; used for digging and grubbing. 
Maximum Certified Gross Weight
  • Absolute maximum allowable gross weight for an aircraft as established by the manufacturer and approved by the FAA. 
Maximum Computed Gross Weight
  • Computed gross weight for an aircraft, obtained from the appropriate performance chart, which is the maximum gross weight appropriate to the applicable circumstance of configuration and/or environmental conditions. 
Maximum Dry Bulb Temperature
  • The highest value for dry bulb temperature measured at the observation site during the preceding 24-hour period. 
Maximum Manageable Area (MMA)
  • The maximum geographic limits of spread within which a wildland fire is allowed to spread. 
Maximum Relative Humidity
  • The highest value for relative humidity measured at the observation site during the preceding 24-hour period. 
May Day
  • International distress signal/call. When repeated three times it indicates imminent and grave danger and that immediate assistance is required. 
  • A combination hoe or cutting tool and rake, with or without removable blades. 
Mean Fire Return Interval
  • Arithmetic average of all fire intervals in a given area over a given time. 
Mean Sea Level (MSL)
  • Average height of the surface of the sea for all stages of the tide over a 19-year period. NOTE: when the abbreviation MSL is used in conjunction with a number of feet, it implies altitude above sea level (e.g., 1000 feet MSL).  Source:  http://glossary.ametsoc.org/wiki/Mean_sea_level
Measured Woody Fuel Moisture
  • Moisture content of the small branch wood and foliage of live woody plants, expressed as a percentage of the oven dry weight of the sample, collected monthly and used to supplement NFDRS modeled outputs. 
Medical Unit
  • Functional unit within the logistics section that is responsible for the emergency medical and occupational health care of incident personnel. Some incident management teams have placed this unit under safety. 
Medium Expansion
  • Foam with an expansion between 21:1 and 200:1. 
Medium-range Forecast
  • Mobile medical treatment and transportation. 
Merged Wildfires
  • Two or more wildfires that burn together to form a single burned area and which, by management action, may be declared merged and managed as a single incident to improve efficiency and simplify incident management processes.

    • Definition Extension: 1) Management can decide to declare wildfires as merged or not.  2)  A merged wildfire requires a Merged Date and association with the remaining active wildfire, i.e. Merged Parent, to be identified correctly in operational and historical data.


Message Center
  • The message center is part of the incident communications center and is collocated or placed adjacent to it. It receives, records, and routes information about resources reporting to the incident, resource status, and administrative and tactical traffic. 
  • A set of standardized procedures and practices that have been peer-reviewed and have received general acceptance by the profession. 
Micro-Remote Environmental Monitoring System (Micro-REMS)
  • Mobile weather monitoring station. Each unit consists of a shipping container, solar panel, battery, temperature/relative humidity sensor, wind mast, wind direction/speed sensor, data logger and radio. A Micro-REMS usually accompanies an incident meteorologist and ATMU to an incident. 
Microscale Fire Pattern Indicator
  • Fire pattern indicators that are generally only visible when viewed within close proximity.
    • Definition Extension; This may include standing nearby, and/or the need to crouch or get down on hands and knees to observe.
Mid-Flame Windspeed
  • The speed of the wind measured at the midpoint of the flames, considered to be most representative of the speed of the wind that is affecting fire behavior. 
Military Operations Area (MOA)
  • Military Operations Area found on aeronautical charts. 
  • A unit of pressure equal to a force of 1,000 dynes per square centimeter. (A dyne is the force that would give a free mass of one gram an acceleration of one centimeter per second per second).  Source:  http://glossary.ametsoc.org/wiki/Millibar 
Mineral Ash
  • The residue of mineral matter left after complete combustion of wood (wood ash) or other organic material; consists largely of oxides, carbonates, and phosphates of Ca, K and Mg, together with other compounds. 
Mineral Soil
  • Soil layers below the predominantly organic horizons; soil with little combustible material. 
Minimum Cost Suppression Alternative
  • The alternative that achieves incident objectives, consistent with priority for firefighter and public safety, and is least expensive when considering expected costs for fire suppression and emergency stabilization and/or rehabilitation. 
Minimum Dry Bulb Temperature
  • The lowest value for dry bulb temperature measured at the observation site during the preceding 24-hour period. 
Minimum Impact Suppression Tactics
  • See Minimum Impact Suppression Techniques
Minimum Impact Suppression Techniques (MIST)
  • The application of strategy and tactics that effectively meet suppression and resource objectives with the least environmental, cultural and social impacts. 
    • Also known as Minimum Impact Suppression Tactics
Minimum Relative Humidity
  • The lowest value for relative humidity measured at the observation site during the preceding 24-hour period. 
Miscellaneous Fire
  • Fire of known cause that cannot be properly classified into any of the eight standard causes of fires. 
Mission Assignment
  • A work order issued by FEMA, with or without reimbursement, which directs another federal agency to utilize its authorities and the resources granted to it under federal law in support of state, local, tribal, and territorial government assistance.
  • Modifying the environment or human behavior to reduce potential adverse impacts of from a natural hazard.
Mitigation Actions
  • Actions that are implemented to reduce or eliminate (mitigate) risks to persons, property or natural resources. These actions can be undertaken before and during a wildfire. Before a fire actions can include fuel treatments, creation of fuel breaks or barriers around critical or sensitive sites or resources, and vegetation modification and structural changes to increase the chance a structure will survive a wildfire with or without active protection (sometimes referred to as defensible space or the home ignition zone). Mitigation actions can also occur during response and can include mechanical and physical tasks, specific fire applications, and limited suppression actions. Such as fireline construction, and creating "black lines" through the use of controlled burnouts to limit fire spread and behavior.
Mix Ratio
  • The ratio of liquid foam concentrate to water, usually expressed as a percent. 
Mixing Chamber
  • A tube, constructed with deflectors or baffles, that mixes foam solution and air to produce tiny, uniform bubbles in a short distance (1 to 2 ft). 
Mixing Height
Mixing Layer
  • The person in charge of fire retardant mixing operations with responsibility for quantity and quality of the slurry and for the loading of aircraft. 
Mobile Radio
  • A two way radio unit on mobile apparatus (instead of base stations), usually semi-permanently attached to the apparatus. 
Mobile Weather Unit Forecast
  • A special weather forecast for a specific incident prepared by a meteorologist on site at or near the incident area. A special fire weather forecast for a specific fire prepared by a meteorologist on site at or near the fire area. 
  • The process and procedures used by all organizations, federal, state and local, for activating, assembling, and transporting all resources that have been requested to respond to or support an incident. 
Mobilization Center
  • An off-incident location at which emergency service personnel and equipment are temporarily located pending assignment, release, or reassignment. 
Mobilization Guide
  • A written description of procedures used by federal, state, and local organizations for activating, assembling, and transporting resources that have been requested to respond to or support an incident. 
  • A simplified or generalized representation of reality; a description, analogy, picture, or hypothesis to help visualize something that cannot be directly observed. 
Model Arson Law
  • Model legislation, recommended by the Fire Marshals' Association of North America and adopted in most states, dealing with the subject of arson. 
Model Fireworks Law
  • Model legislation recommended by the Fire Marshals' Association of North America and adopted by many states, regulating display of fireworks. 
Modular Airborne Firefighting System (MAFFS)
  • A manufactured unit consisting of five interconnecting tanks, a control pallet, and a nozzle pallet, with a capacity of 3,000 gallons, designed to be rapidly mounted inside an unmodified C-130 (Hercules) cargo aircraft for use in cascading retardant chemicals on wildfires. 
Moist Adiabatic Lapse Rate
  • Rate of decrease of temperature with increasing height of an air parcel lifted at saturation via adiabatic process through an atmosphere in hydrostatic equilibrium. Rate varies according to the amount of water vapor in the parcel and is usually between 2.0 and 5.0 degrees F per 1000 feet (3.6 and 9.2 degrees C per 1000 meters). 
Moisture of Extinction
  • The fuel moisture content, weighed over all the fuel classes, at which the fire will not spread. Also called extinction moisture content (EMC). 
  • A turret-type nozzle usually mounted on an engine. 
  • The orderly collection, analysis, and interpretation of environmental data to evaluate management's progress toward meeting objectives, and to identify changes in natural systems. Monitoring is also conducted on wildland fires to observe fire effects, fire behavior, or both. For example, the work done by Fire Effects Monitor (FEMO) or Field Observer (FOBS) positions. 
Monsoon Climate
  • Climate characterized by (a) a long winter-spring dry season which includes a "cold season" followed by a short "hot season" immediately preceding the rains, (b) a summer and early autumn rainy season which is usually very wet (but highly variable from year to year), and (c) a secondary maximum of temperature immediately after the rainy season.
Mop Up
  • Extinguishing or removing burning material near control lines, felling snags, and trenching logs to prevent rolling after an area has burned, to make a fire safe, or to reduce residual smoke.
    • Definition Extension: 1) Mopup is one word if used as a noun (the crew will do mopup); 2) Mop up is two words if used as a verb (mop up the fire) or as an adjective (mop up crew).
Mop Up Crew
  • A portion or all of a regular fire crew assigned to mop up work after the fire or a portion of the fire has been contained or controlled. 
Mop Up Time
  • Elapsed time from containment or control of a fire until mopup is complete. 
  • The intermingling of plant communities and their successional stages in such a manner as to give the impression of an interwoven design. 
Move Up
  • System of redistributing remaining personnel and equipment following dispatch of other forces among a network of fire stations to provide the best possible response within the fire department's direct protection area in the event of additional calls for emergency assistance. 
Move Up Method
  • Progressive method of fireline construction on a wildfire without changing relative positions in the line. Work is begun with a suitable space between workers; whenever one worker overtakes another, all of those ahead move one space forward and resume work on the uncompleted part of the line. The last worker does not move ahead until work is completed in his/her space. Forward progress of the crew is coordinated by a crew boss. 
Multi-Agency Coordinating Group (MAC Group)
  • A national, regional, or local management group for interagency planning, coordination, and operations leadership for incidents. Provides an essential management mechanism for strategic coordination to ensure incident resources are efficiently and appropriately managed in a cost effective manner. 
Multi-Agency Coordination (MAC)
  • A generalized term which describes the functions and activities of representatives of involved agencies and/or jurisdictions who come together to make decisions regarding the prioritizing of incidents, and the sharing and use of critical resources. The MAC organization is not a part of the on-scene ICS and is not involved in developing incident strategy or tactics. 
Multi-Agency Incident
  • An incident where one or more agencies assist a jurisdictional agency or agencies. May be single or unified command. 
  • A VHF/AM aircraft radio frequency (122.9 MHz) assigned by the FAA for use in air-to-air communications. 
Multijurisdiction Incident
  • An incident requiring action from multiple agencies that have a statutory responsibility for incident mitigation. In ICS these incidents will be managed under unified command. 
Multiple Fire Situation
  • High fire frequency over a short period of time in an administrative unit, usually overtaxing the normal initial attack capability of the unit. 
Multiple Fire-Day
  • In FireFamily Plus, a day with both a weather observation and a number of fires equal to or greater than that determined by the user to be a significant workload. 
Multiple Points of Origin
  • Two or more separate points of fire origins at a fire scene; strong indication of arson. 
Mutual Aid
  • Assistance in firefighting or investigation by fire agencies, without regard for jurisdictional boundaries. 
Mutual Aid Agreement
  • Written agreement between agencies and/or jurisdictions in which they agree to assist one another upon request, by furnishing personnel and equipment. 
Mutual Threat Zone
  • A geographical area between two or more jurisdictions into which those agencies would respond on initial attack. Also called mutual response zone or initial action zone.