A homosexual woman. (slander)
Man: "How did I know my girlfriend would run off with a clam bumper?"
"Gee, I never would've guessed that Rosie O'Donnell was a clam bumper.", he said sarcastically.
"you two clam bumpers wanna be alone?"
One definition of lesbians, (clam meaning vagina) insisting that the two women have sex by rubbing one of their vaginas against the others vagina.
Cindy and Martha love eachother, they are probably clam bumpers.
Cassie Balleza from chowchilla that is really RANK. she smells like cottage cheese!!!!! shes a fat stupid bitch and often fucks sara merical, also a clam bumper who smokes oregano and thinks its bud!
Sarah and cassie fuck when they are together