eleventh hour vs moment

eleventh hour and moment both are nouns.

Word	Noun	Adjective	Verb	Adverb
eleventh hour	Yes	No	No	No
moment	Yes	No	No	No

As nouns, moment is a hypernym of eleventh hour; that is, moment is a word with a broader meaning than eleventh hour:

Other hypernyms of eleventh hour include instant, minute, second.

eleventh hour (noun)	moment (noun)
the latest possible moment	having important effects or influence
	the n-th moment of a distribution is the expected value of the n-th power of the deviations from a fixed value
	a turning force produced by an object acting at a distance (or a measure of that force)
	a particular point in time
	an indefinitely short time
	at this time