A person whom turns on you and screws you over for a girl, video games, or money. Any malicious act against you or your friends can qualify the perpetrator to be called a dirty rat from a dirty sewer.

Also can be called a 'filthy rat' or 'the filthiest rat' or 'the dirtiest rat from the dirtiest sewer' or just plain 'rat'
Guy 1- "That Chris is a dirty rat from a dirty sewer."
Guy 2- "Yeah, the filthiest rat from the dirtiest sewer."
Guy 3- "What a dirty rat!"
by Rat Keeper March 8, 2011
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