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1.
N. A crass yet novel insult asserting that a person is, in essence, the personified act of male masturbation. Best used in moderation and in lieu of traditional slander due to its absurdity and memorable sting.
1 .Hey Jimmy Whack, what are we wearing tonight?

2. Did you see that guy cut in line? What a Jimmy Whack!
by Europe Penyen January 24, 2010
 
2.
A no longer functioning penis.
Hey, Sephy's Jimmy whack!
by Rhendal September 21, 2003