tail end vs ass

tail end and ass both are nouns.

Word	Noun	Adjective	Verb	Adverb
tail end	Yes	No	No	No
ass	Yes	No	No	No

As nouns, tail end and ass are synonyms defined as:

tail end (noun)	ass (noun)
the fleshy part of the human body that you sit on	slang for sexual intercourse
any projection that resembles the tail of an animal	hardy and sure-footed animal smaller and with longer ears than the horse
the time of the last part of something	the fleshy part of the human body that you sit on
	a pompous fool