when a man stands with his legs spread a bit and swings his ball sack so that they slap his grungle area.
i dared my friend to do something embarrassing and he pulled his pants down and showed me the grundle slap.
by James Hill January 15, 2008
A guy makes his pants tight so that the area above his dick if firm (usually by sitting down, you know what i mean) and then slaps it with his hand, in what would seem to be painful but is completely not.
by xhollywoodx January 13, 2006