altitude vs altitudinous

altitude is a noun but altitudinous is not a noun.

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

altitude (noun)	altitudinous (noun)
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)

altitude (adjective)	altitudinous (adjective)
	indefinitely high; lofty