Where your fucking cold or you have the gay-ass goose bumps, your nipples get fucking hard and pointy. Sometimes called pointy toys.
Man 1 "Dude did you see that slut with the pointy toys?" Man 2 "yeah you could see them through her white wet shirt!"
An early-warning system deployed by women to indicate A) they are feeling cold or B) they are feeling horny. The skill lies in the interpretation.
If you see a woman with erect nipples try asking: "Are those two frozen peas in your bra or would you like me to fuck you?"