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3.
a girl that oral sex to a guy
yo, she got dirty knees!
by CivicChikk July 24, 2003
 
1.
Clear evidence of performing fellatio.
When they came out of the bathroom her hair was mussed; she might as well have had dirty knees.
by tman March 11, 2004
 
2.
To Suck someones penis, while on your knee
yo, she be getting her knees dirty.

Yo she got dirty knees.
by kibblasona January 05, 2006
 
4.
(noun)
when a girl gives a boy head in a porta-potty, which results in her knees being covered in fecal material or piss. Once the man blows a load, and they clean up, the girl needs to use soap and water before her knees are to the original skin color.
Samantha has some dirty knees after the porta-potty incident.
by jacobito May 13, 2007