- A form of softwood indigenous to temperate zones, used principally for interior trim and framing. Varieties include Douglas fir, silver fir, balsam fir, and white fir.
- Although used most often to refer to Douglas fir, which is also a pseudo-fir, a general term forany of a number of species of conifers, including the true firs.
- (written as FIR)factor intensity reversal.
- acronym forFactor intensity reversal (written as FIR)
- noun a tree which does not lose its leaves in winter (such as a pine, spruce, etc.)
- acronym forflight information region (written as FIR)
- noun airspace with defined limits which has an air traffic control information and alerting service.
Origin & History of “fir”
As with many Indo-European tree-names, fir is a widespread term, but it does not mean the same thing wherever it occurs. Its prehistoric Indo-European ancestor was *perkos, which in Latin became quercus, the name for the ‘oak’. Nor was the application confined to southern Europe, for Swiss German has a related ferch ‘oak wood’. But by and large, the Germanic languages took the term over and applied it to the ‘pine’: German föhre, Swedish fura, and Danish fyr all mean ‘pine’. So also did Old English furh (known only in the compound furhwudu ‘pine-wood’), but this appears to have died out. It was replaced semantically by pine, but formally by middle English firre, a borrowing from the Old Norse form fyri- (also known only in compounds). This was used as a name not for the ‘pine’, but for the ‘fir’ (which in Old English times had been called sæppe or gyr).