When a female celebrity "accidently" lets her nipple show or has her whole boob slip out. Check pictures of Lindsey Lohan.
When a braless female's nipple accidentaly slips out from under a loose-fitting garment
Hold up, pause it there. Yup, total nip slip!
When a nipple slips in to view.
She walked out on stage with her tit falling out, it was a hell of a nip slip!
When a nipple (more often than not, the nipple of a woman) slips out of an article of clothing, partially or fully, and is noticed by someone else.
She destroyed the nip slip photograph almost immediately
To have the nipple showing on accident. Most common in public or on live t.v.
Don had such a nip slip the other day, he got embarrassed because he was on live t.v.
Seriously. Has nobody ever told these brainless celebrity twats that there exists a garment called BRASSIERE? What kinds of exhibitionist morons go around wearing clothes which might reveal a private body part at any given moment, anyway?
Tara Reid: your nipple is ugly.
A nip slip is typically when someone's nippers slip out from their clothes and flashes the people watching
Person1:* sees friends nip slip from her bikini *
Person 1: HEY!! Your nip needs covering !
*jumps onto friend to prevent her from flashing the fishes in the tank*
Person2:OUCH! U could have just throw a towel at me, ur heavy!!!