When you absolutely plough the shit out of the side of someone's thigh with your knee, hence named because they will be walking like a grandad for the rest of the day.
by Frankoyo December 02, 2013
by Steelbeast November 01, 2020
by grandads girl LOL January 21, 2009
by Jimby Bobbinson January 23, 2018
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by Rugbyface10 December 17, 2018
by Chicken83 April 02, 2007