ALT vs altitude

ALT and altitude both are nouns.

Word	Noun	Adjective	Verb	Adverb
ALT	Yes	No	No	No
altitude	Yes	No	No	No

As nouns, ALT and altitude are synonyms defined as:

ALT and altitude: angular distance above the horizon (especially of a celestial object)

Other synonyms of ALT include EL, elevation.

ALT (noun)	altitude (noun)
angular distance above the horizon (especially of a celestial object)	elevation especially above sea level or above the earth's surface
	angular distance above the horizon (especially of a celestial object)
	the perpendicular distance from the base of a geometric figure to the opposite vertex (or side if parallel)