Protruding nipples that look like they can cut diamonds. Usually visible around colder climates and erotic situations.

Nip rocks can be seen underneath shirts, which automatically qualify the girls to be smuggling skittles
Bless that girl with them visible nip rocks. She look like she be smuggling skittles.
by yellowboy February 12, 2004
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When ur titty gets as hard as a rock
Bro yesterday I was taking a shower and all of a sudden my nipple was hard as a rock broooooo it’s a Rock Nip
by BeastMasta69 December 6, 2017
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