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When you go to have sex with a guy and realize he has no balls.
I was 69'ing with this one guy and his flat sack hit me in the face.
by hen-peter May 29, 2011
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One who has no balls, a neutered dog. Just a sack with no balls.
Hey wade you have no balls you are a flat sack
by Cuevous May 28, 2016
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