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1.
When you store an object or objects behind your knee, whilst lifting the apropriate leg aloft to keep said object(s) in place.
"Yeh, i didn't have any hands free, so i used my Knee-Bag for a bit"
by Phatang May 12, 2009
 
2.
a tea bagging that occurs on one's knee, as opposed to one's mouth in a regular tea bag
Madison knee bagged Chase today for no apparent reason
by superwaffles March 06, 2010
 
3.
a derogatory term for a person; equivalent to asshole, bitch or other terms
Son of a Knee Bag.
Mother Knee Bag.
Fuckin Knee Bag.
by artchicany March 17, 2004