Waist Bandit

A female who's attractiveness forces you to tuck your boner into your waist band.

John: "dude Emily Ratajkowski is such a waist bandit!"
Sarah: " that's offensive"
John: "cuz every time I see her, I gotta hide my boner!"

Waist Bandit

Another term for an erection.

Ashley: Hey, did you see John last night? He had a waist bandit.

Brittany: Oh, that was John?