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1.
1. Adapted to urban environments, rats thrive in the shadows and grime.

2. Spray can in tail, the rat leaves his signature on the walls and buildings of the urban jungle.

Someone tagged the building, I smell a Dirty Rat.

by Giga-bat May 21, 2008
 
2.
A sexual technique where the woman lies on her back and the gentleman squats over her face while lowering his scrotum into her mouth. The gentleman must simultaneously shimmy his penis back and forth as if to simulate a rat's tail. The gentleman must also lower his hairy anus onto the woman's nose. For those who go the extra mile one can imitate a rat's gnawing sneer.
Rishbah: I was going to break up with her last night but then she let me hit her with the "dirty rat".

Kishdam: NICCCEEEEEEE
by Unconventional Methods October 07, 2011
 
3.
Brady Lavin. of or relating to Brady Lavin
Brady Lavin is a dirty rat
by Anonymous May 28, 2003