When the ball sack shrivels up and the dick hangs over it, leaving a protrusion from your pants, thus looking like a boner when indeed you do not have one. Usually ball boners make it seem like you have a small dick because of the unerected penis sitting on top of the ball sack.
After harry gets out of the pool, his ball boner revealed his dick to other girls who thought it was tiny.
by kevinaninno December 4, 2010
An erection on a male who has only one testicle. Typically displayed in online chats or ASCII form as a U plus a seemingly appropriate number of pipes (|) followed by a D to indicate the head. The head may be preceded by two or more slashes (\) if a pulled back foreskin is present.
by stbn January 3, 2010
by Assfucker123 December 4, 2016