piece of tail vs coition

piece of tail and coition both are nouns.

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

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

piece of tail: slang for sexual intercourse
coition: 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)	coition (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