Penstruation: menstruation that is brought on by penile penetration, despite the subject being pre or post menstruation. Penstruation is often discovered, post-coitus, due to bloody sheets (or other stained lovemaking surfaces). Anecdotally: women who have experienced penstruation report that it is associated with passionate, vigorous (condomless) sex, a fairly well endowed partner, and voluminous deposits of sperm, which may be why neither party usually minds the bloody after-effects too much.
"So, in a case of penstruation, who is responsible for washing the sheets, the girl or the guy?"

"Oh, the guy, of course."
by jacandy December 28, 2011
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