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2.
A delicate sexual maneuver also known as the switch. When doing a girl from behind, you quickly move out of the way and let your buddy (the silent partner) finish up. Often preformed when you are about to break up with the said girl.
I was about to break up with her, so my roommate gave me $20 to pull a silent partner on her.
by Woobert August 29, 2005
 
1.
The man or woman who was already in a quiet public restroom taking a dump, and who stops taking a dump when you enter the restroom or sit down beside them, presumably because they don't want you to hear them taking said dump. They usually wait until you leave to resume their business.
I entered the men's room and sat down for a shit in an available stall. The room was empty, except for one silent partner in the stall next to me. When I was finished, I washed my hands and left, but as the door closed behind me, I heard the whalesong-like sounds of my silent partner resuming his bowel movement.
by Orion1972 March 08, 2013
 
3.
A condition of the butthole, often times mis-categorized as "Jungle Booty," "Swamp Ass," or any other wet-ass syndrome. A silent partner, however, is the stinky residookie or even condensate left after a 3-hour long shit and possible prolapsed rectum. See also: seepage.
Jim: Man, someone cut one, it better not be that baby over there.

Tina: I don't think so, it doesn't seem to be getting any stronger in intensity.

Kendall: Guys, I gotta confess...its me. Well, it's not technically me, it's my silent partner.

Tina: Typical
by pbr3000 April 09, 2009