look up any word, like blumpkin:
 
1.
A harmless prank where one flaps the palm of their hand side to side, like a salmon, against the insides of another persons thighs from behind. The higher up the thigh, the dirtier the dirty salmon.
Dude, can you believe he just dirty salmoned the mormon chick?

Yeah man, I think he's going to go to jail.
by Smilikymeat April 10, 2011
 
2.
A sexual encounter where one climbs on top of their mate and wiggles vigorously up and down. As if swimming upstream.
while laying there after sex my boyfriend began to give me the dirty salmon, it got awkward!
by FPIA May 20, 2010