1 definition by saggy sack

Balls. When sitting correctly, a mans testes may cover the anus and becoming a 'mud flap'. Also, when two are engaged in intercourse in the missionary position, the mans testes may cover the woman's anus and therefore becoming the woman's 'mud flap'.
Woman: What's a mud flap?
Man: I'll show you...
by saggy sack October 26, 2010

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