ass vs sex act

ass and sex act both are nouns.

Word	Noun	Adjective	Verb	Adverb
ass	Yes	No	No	No
sex act	Yes	No	No	No

As nouns, sex act is a hypernym of ass; that is, sex act is a word with a broader meaning than ass:

ass: slang for sexual intercourse
sex act: sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur

ass (noun)	sex act (noun)
slang for sexual intercourse	sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur
hardy and sure-footed animal smaller and with longer ears than the horse
the fleshy part of the human body that you sit on
a pompous fool