when someone slaps another person in the same fashion as a bitch slap, except with more seriousness and with an intent to harm.
bob: "god damn! that dude just bitch slapped that man to the ground!"
bill: "no bob, that man just got grandfather slapped."
bill: "no bob, that man just got grandfather slapped."
by grandfather3 November 3, 2010
Get the grandfather slapmug.