coitus vs piece of tail

coitus and piece of tail both are nouns.

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

As nouns, piece of tail is a hyponym of coitus; that is, piece of tail is a word with a more specific, narrower meaning than coitus:

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: slang for sexual intercourse

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