rump vs posterior

rump and posterior both are nouns.

Word	Noun	Adjective	Verb	Adverb
rump	Yes	No	No	No
posterior	Yes	Yes	No	No

As nouns, rump and posterior are synonyms defined as:

rump (noun)	posterior (noun)
the part of an animal that corresponds to the human buttocks	the fleshy part of the human body that you sit on
the fleshy part of the human body that you sit on	a tooth situated at the back of the mouth
fleshy hindquarters; behind the loin and above the round

rump (adjective)	posterior (adjective)
	located at or near or behind a part or near the end of a structure
	coming at a subsequent time or stage