piece of tail vs coitus

piece of tail and coitus both are nouns.

Word	Noun	Adjective	Verb	Adverb
piece of tail	Yes	No	No	No
coitus	Yes	No	No	No

As nouns, coitus is a hypernym of piece of tail; that is, coitus is a word with a broader meaning than piece of tail:

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

piece of tail (noun)	coitus (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