Green’s Dictionary of Slang

nip n.4

[abbr.]

the nipple.

[US] ‘Kansas City Kitty’ [comic strip] in B. Adelman Tijuana Bibles (1997) 54: He squeezed and tickled the little nips until I thought I would go mad.
[US]Southern & Hoffenberg Candy (1970) 145: She was [...] somewhat annoyed with the way her pert little nips kept pulsing and pouting.
[US]B. Jackson Get Your Ass in the Water (1974) 150: Say, Lil had nips on her titties about the size of your thumb, / she had somethin’ between her legs would make a dead man come.
[US]B. Jackson Get Your Ass in the Water (1974) 191: She had nips on her titties sweet as plums, / she had hair on her cock [that would] make a dead man come.
[US]D. Jenkins Semi-Tough 222: Barbara Jane’s lungs [...] have the good nips.
[US]S. Morgan Homeboy 281: ‘My eyes’ — she pointed to her baby blues — ‘are the windows of my soul. My nips’ — she tweaked them — ‘its antennae.’.
[US]J. Stahl Permanent Midnight 114: I’d have to twist and pinch the incredibly plump old-lady nips.
[US]G. Pelecanos Right As Rain 42: She did have a nice set, though, the kind that stood at attention, with sharp pink-button nips.
Skins ser.1 ep.1 [TV script] ‘Hi, Nips.’ ‘Stop calling me, Nips. It’s a funny name.’ ‘I’ve seen a few nipples, Nips, and yours are fucking hilarious’.
[UK]J. Fagan Panopticon (2013) 160: [of a man] ‘You’ve got stiff nips,’ I tell him.

In compounds

nip-slip (n.)

the involuntarily display of a nipple, usu. via an already revealing garment.

[Scot]C. Brookmyre Be My Enemy 99: ‘More than a nip-slip [...] it’s a lot more than your usual blurry down-blouse.’ ‘Confirmed visible nipple?’ ‘In colour.’.