A vagina so filthy that it has begun to look like a dirt matted leather wallet. A Dirt Wallet will often carry diseases and should be avoided at all costs.
Dirt Wallets should only be approached after a thorough cleaning has been completed, and tests have been performed to ensure the Dirt Wallet is disease free.
Guy #1 - "Hey did you hook up with that girl last night?"
Guy #2 - "No, she had a total Dirt Wallet. I almost threw up."