fir

plural firs

1. countableA conifer of the genus Abies.

   A beech wood with silver firs in it rolled down the face of the hill, and the maze of leafless twigs and dusky spires cut sharp against the soft blueness of the evening sky.

   1907 January, Harold Bindloss, chapter 1, in The Dust of Conflict, 1st Canadian edition, Toronto, Ont.: McLeod & Allen, →OCLC

2. countableAny pinaceous conifer of related genera, especially a Douglas fir (Pseudotsuga) or a Scots pine (Pinus sylvestris).

   I can almost smell the fir scent… resinous, pungent.

   1991, Paul Chadwick, Concrete: American Christmas, Dark Horse Books

   1 more example

   we shall find a spot that is sheltered and snug enough, sir. There is a dry fir-wood just ahead, if I remember rightly.

   1954, J. R. R. Tolkien, chapter 3, in The Lord of the Rings

3. uncountableWood of such trees.

   Synonyms: firwood

1. abbreviationinitialismnot comparablecomputingInitialism of finite impulse response; that has impulse response (or response to any finite length input) of finite duration.

plural FIRs

1. abbreviationcountableinitialismuncountableaeronauticsInitialism of flight information region; a specified region of airspace in which a flight information service (FIS) and an alerting service (ALRS) are provided.
2. SingaporeSouth AsiaabbreviationcountableinitialismuncountablegovernmentInitialism of first information report.
3. abbreviationuncountableAbbreviation of far infrared or far infrared radiation.