It's when you grab the skin between your hanging balls and your cock and then tighten your grip all the way up to your balls forcing them to really stick out, this makes your sac look veiny and bumpy like the top of a brain.
I asked my girl to examine a spot in my testes, when she came in for a closer look, I tightened up my grip and hit her in the eye with the brainer.
by allen powell January 16, 2006

Jim: Do you have to put your marshmallow in the fire?
Clark: Dude, it's a no brainer, as a rule of thumb campers should put their marshmallow in the fire.
Clark: Dude, it's a no brainer, as a rule of thumb campers should put their marshmallow in the fire.
by Nosseir April 23, 2007

by nick_g August 16, 2011

by Not Joe Bereta April 24, 2013

An easy decision made using the brain. As opposed to a 'no brainer', an incorrect term seeing as how all decisions are made using the brain, as pointed out by SourceFed's brilliant Joe Bereta.
by anIrishViking April 24, 2013

The decision was a brainer
by Sourcefed fan15 April 24, 2013

