When a chick's nipples are hard and they stick out prominently from under her clothes, just like the "turkey's ready" indicators on a succulently done butterball.
This is incredibly hot and every guy within miles will notice and get a half-stiffy just from seeing that. Usually happens when it's cold or she's aroused and she is wearing a tank top or other tight shirt and a thin or (ESPECIALLY) no bra, which is up there with the hottest thing ever!
Guy 1: OMG, did you see Stephanie's tits this morning when the air conditioning kicked in??!
Guy 2: See her?? I rubbed one out in the men's room to her Turkey's Ready!!