When a female/any person with a vagina rubs her vaginal area on someone else, especially while that person is sleeping, passed out or otherwise occupied.
Coffee grind is also less commonly used to describe rubbing the vaginal area on a willing partner during foreplay.
"Kelly, don't bother coffee grindin' that guy - he's just pretending to be asleep!"
"Quick, grab the camera! Katie's giving Brad a mad coffee grind!"
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