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)
Ultra High Frequency (UHF-FM)
  • Radio frequencies from 300 Megahertz (MHz) to 3,000 MHz with a normal range of less than 50 miles. Radio frequency common to military aircraft and used in the logistics radio system. The most common frequencies used by fire and public safety are from 406 MHz to 512 MHz. 
Unacceptable Risk
  • Level of risk as determined by the risk management process which cannot be mitigated to an acceptable safe level. 
Uncontrolled Airport
  • Airport not having an approved agency with radio communications to direct aircraft take-offs and landings. 
Uncontrolled Fire
  • Any fire which threatens to destroy life, property, or natural resources, and (a) is not burning within the confines of firebreaks, or (b) is burning with such intensity that it could not be readily extinguished with ordinary tools commonly available. 
  • A fire that consume surface fuels but not the overstory canopy.
Undercut Line
  • A fireline below a fire on a slope. Should be trenched to catch rolling material. Also called underslung line.
Understory Burning
  • Prescribed burning under a forest canopy.
Unified Area Command
  • A unified area command is established when incidents under an area command are multijurisdictional. 
Unified Command
  • In ICS, unified command is a unified team effort which allows all agencies with jurisdictional responsibility for the incident, either geographical or functional, to manage an incident by establishing a common set of incident objectives and strategies. This is accomplished without losing or abdicating authority, responsibility, or accountability. 
Unified Ordering Point (UOP)
  • Single location through which all incident resource orders are processed.
  1. The organizational element having responsibility within a functional area in the incident command structure such as operations, planning, logistics or finance.
  2. A generic term that represents an organizational entity that only has meaning when it is contextualized by a descriptor, e.g. jurisdictional.
    • Definition Extension:  When referring to an organizational entity, a unit refers to the smallest area or lowest level.  Higher levels of an organization (region, agency, department, etc) can be derived from a unit based on organization hierarchy.
Unit Identifier
  • A code used within the interagency wildland fire community to uniquely identify a particular government organizational unit or a non-government organization recognized by NWCG as a wildland fire cooperator.
Unit, Home
Unit, Jurisdictional
  • The governmental entity having overall land and resource management responsibility for a specific geographical area as provided by law.
    • Definition Extension: 1) Ultimately responsible for the fire report to account for statistical fire occurrence; 2) Responsible for setting fire management objectives; 3) Jurisdiction cannot be re-assigned by agreement; 4) The nature and extent of the incident determines jurisdiction (for example, Wildfire vs. All Hazard); 5) Responsible for signing a Delegation of Authority to the Incident Commander.
Unit, Protecting
  • The entity responsible for providing direct incident management and services to a given area pursuant to its jurisdictional responsibility or as specified by law, contract or agreement.
    • Definition Extension: 1) Protection can be re-assigned by agreement; 2) The nature and extent of the incident determines protection (for example - Wildfire vs. All Hazard.)
Unit, Provider
  • Any government organization that is a source of resources for response or mutual aid support to an incident, whether in the field, at the scene of an incident, or operations center.  This includes government organizations that administer contracts or agreements for resources.
Unity of Command
  • The concept by which each person within an organization reports to one and only one designated person. 
Unity of Effort
  • A command philosophy that encourages leaders to work together to find common ground and act in the best interest of those responding to the incident, the public, and the resources that are threatened. 
Unlined Fire Hose
  • Hose commonly of cotton, linen, or synthetic fiber construction without rubber tube or lining, often used for wildfires because of its light weight and self protecting (weeping) characteristics; such hose is attached to first-aid standpipes in buildings. At a specified flow, friction loss in unlined hose of a stated diameter is about twice that of lined fire hose. 
Unplanned Ignition
Unprotected Lands
  • Areas for which no fire organization has responsibility for management of a wildfire authorized by law, contract, or personal interest of the fire organization (e.g., a timber or rangeland association).
Upper Level (Cold) Low
  • Upper Level Disturbance, Cold Low Aloft: A circulation feature of the upper atmosphere where pressure, at a constant altitude, is lowest. Winds blow counter-clockwise around the center in an approximately circular pattern. Upper level lows are usually quite small. The mechanics of these upper lows is such that a pool of cool moist air always accompanies their development. There is often no evidence of low pressure at the earth's surface. An upper low may exist above a surface high pressure system. 
Upper Level (Cold) Trough
  • Trough, Trough Aloft, Upper Level [Cold] Low: An elongated area of relatively low pressure, at constant altitude, in the atmosphere. The opposite of an upper level ridge. Upper level troughs are usually oriented north-south with the north end open. That is, air currents moving from west to east around the earth flow around three sides of the trough then turn eastward rather than toward the west, as in the case of a closed circulation. A large upper level trough may have one or more small upper level closed low circulation systems within it. 
Upper Level High
  • Upper High, High Aloft, Upper Level Ridge: A circulation feature of the upper atmosphere where pressure, at a constant altitude, is higher than in the surrounding region. Winds blow clockwise around an upper level high. Air in an upper level high is usually subsiding. This results in comparatively warm dry air with light winds over a large area. An upper level high may exist without there being high pressure at the earth's surface. 
Upper Level Ridge
  • (Upper Level High, Ridge Aloft) An elongated area of relatively high pressure, at a constant altitude, in the atmosphere. The opposite of an upper level trough. Upper level ridges are often oriented north-south, alternating between upper level troughs, however, during summer they may assume random orientations and vast dimensions. 
Use Level
  • The appropriate ratio of liquid foam concentrate to water recommended by the chemical manufacturer for each class of fire, usually expressed as a percent (such as 0.5%). 
Use of Wildland Fire
Useful Load
  • Maximum computed gross weight minus equipped weight of a helicopter.