Nipple slip

nipple slip 

Where a woman's nipple is unintentionally exposed, either partially or completely.

nipple slip 

The most common sort of celebrity oops picture, where a dress or top slips to the side revealing some or all of a nipple. Most famous nipple slips include about 101 different Paris Hilton slips (intentional) and the imfamous Tara Reid slip that exposed the horrible results of a bad breast enhancement

nipple slip 

In the non-nude world, this is where a girl exposes a nipple unintentionally, as they are never suppose to show anything.