Definitions by Dirty Cather

Clamshell 

The act of picking items up with your butt cheeks. Mimicking the action of a loader equipped with a clam shell bucket

Works best when the male is lying on his back and girl clamshells his penis off his pelvic area.

Just Go With It Movie Coconut scene

Clamshell by Dirty Cather July 3, 2011