f.i.s.c.
- n a secret federal court created in 1978 by the Foreign Intelligence Surveillance Act; responsible for authorizing wiretaps and other forms of electronic surveillance and for authorizing searches of suspected spies and terrorists by the Department of Justice or United States intelligence agencies
f clef
- n a clef that puts the F below middle C on the fourth line of a staff
f layer
- n the highest region of the ionosphere (from 90 to 600 miles up) which contains the highest concentration of free electrons and is most useful for long-range radio transmission
f number
- n the ratio of the focal length to the diameter of a (camera) lens system
f region
- n the highest region of the ionosphere (from 90 to 600 miles up) which contains the highest concentration of free electrons and is most useful for long-range radio transmission
fa
- n the syllable naming the fourth (subdominant) note of the diatonic scale in solmization
faa
- n an agency in the Department of Transportation that is responsible for the safety of civilian aviation