kryptotite

A girl (or guy) who is so tight that kryptonite is required to penetrate and/or tap that.

or

A virgin

or

To emphasize how hot a person is.

"Oh man, that girl is kryptotite"

"I was with that hot ass girl last night. Let's just say she was kryptotite."

"Holy shit, she's kryptotite!"

by Grant McUnit December 6, 2010