When you have a hard-on and you accidentally contort your penis in a way that causes discomfort or pain.
Friend 1: Dude, I had the biggest boner yesterday after school and when I climbed over a fence to take a shortcut to my house, my dick felt like it broke in half.

Friend 2: Bro, sounds like a total shaft snapper.
by MattyK717 November 5, 2015
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