absolute ceiling vs ceiling

absolute ceiling and ceiling both are nouns.

Word	Noun	Adjective	Verb	Adverb
absolute ceiling	Yes	No	No	No
ceiling	Yes	No	No	No

As nouns, ceiling is a hypernym of absolute ceiling; that is, ceiling is a word with a broader meaning than absolute ceiling:

absolute ceiling: the maximum altitude at which an airplane can maintain horizontal flight
ceiling: maximum altitude at which a plane can fly (under specified conditions)

absolute ceiling (noun)	ceiling (noun)
the maximum altitude at which an airplane can maintain horizontal flight	the overhead upper surface of a covered space
	(meteorology) altitude of the lowest layer of clouds
	maximum altitude at which a plane can fly (under specified conditions)
	an upper limit on what is allowed