When a girl is horny, or cold, her nipples will get hard. When you can see hard nipples under a shirt, this is called nippin.
"Dayum! That foin bitch fuckin nippin dawg!"
when somebody's nipples are hard.
"are you cold" "no" "then why you nippin'?"
When your nipples get hard and/or show through your shirt.
"Why are you nippin' so much, girl?" "It's cold in here! Plus I've nipped my whole life!"
When a girls nipple become erect a point out through their shirt for all to see.
Scum: "Yo did you see mrs.mcdonnell nippin today?"
Flie: "No what do you mean?"
Nose Picker: "Her point nipples are poking through her shirt."
Birds Nest" "Yea shes always nippin, she needs a bra."
When a male and female friend rub their nipples together
Tits McGee and ash hole were nippin
the act of napping/sleeping
John: History was so boring..
Alex: Yeah, I def nipped the whole hour.
Ron: Why didn't you come to Jake's party?
Kevin: I had to work this morning..so I nipped all night.
Paul: Ahh man what were you two doing in that bedroom?!
Luther: We were just nippin, I swear!