heap vs mountain

heap and mountain both are nouns.

Word	Noun	Adjective	Verb	Adverb
heap	Yes	No	Yes	No
mountain	Yes	No	No	No

As nouns, heap and mountain are synonyms defined as:

heap and mountain: (often followed by `of') a large number or amount or extent

heap (noun)	mountain (noun)
a car that is old and unreliable	a land mass that projects well above its surroundings; higher than a hill
a collection of objects laid on top of each other	(often followed by `of') a large number or amount or extent
(often followed by `of') a large number or amount or extent