FIR

Adjective

• Initialism of w:finite impulse response; that has impulse response (or response to any finite length input) of finite duration.

Noun

• Initialism of w:flight information region; a specified region of airspace in which a flight information service (FIS) and an alerting service (ALRS) are provided
• Initialism of {{w}}
• Abbreviation of far infrared or far infrared radiation