Resistance to wetting exhibited by some soils, also called water repellency. The phenomenon may occur naturally or may be fire-induced. It may be determined by water drop penetration time, equilibrium liquid-contact angles, solid-air surface tension indices, or the characterization of dynamic wetting angles during infiltration. 

A concave or cup-shaped char pattern found on the side of fuels exposed to the oncoming fire including small stumps (generally 10 inch diameter and less are more reliable), grass stem ends and terminal ends of brush and tree limbs (generally less than 1/2 inch diameter) that indicate the direction of fire progression at that point. One of the 11 NWCG categories of fire pattern indicators.

Weak or missed area in a retardant drop or in a fireline.

In aviation, the intended direction of horizontal flight.

A fire that persists through the winter months until the beginning of fire season.

A chemical or mixture that may present an unreasonable risk of injury to health or the environment.

A tank, usually collapsible, used as a reservoir in the relay of water from one fire pump to another.

Technique of landing specifically trained and certified firefighters from hovering helicopters; involves sliding down ropes with the aid of friction-producing devices.

The study of the effects of fire on living organisms and their environment.

A turret-type nozzle usually mounted on an engine.