What is "bearded clam"

Usage examples of "bearded clam".

I mean, they never showed guys gettin right down and eating hair pie, munchin the ole bearded clam, you know what I mean, but some of those ladies had laigs went right up to their chins, you know what the motherfuck I'm talkin about?

And yes, he can see Mary Jackson's pussy, that highly sought-after part of the female anatomy that was known, in those dim old junior high school days, as 'the bearded clam'.