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1) When A Girl/Guy uses their grandmother to avoid any potential romantic advances

2)When a conversation between someone and a potential date is interupted by either of the people's grandmother
Kenny: Dude i was gonna go talk to this hot girl but then she grabbed her grandmother

Orlando: Dude major grandma

Mike: I was totally about to get laid but then my grandma pulled up and gave me clean underwear

Shanon: That's grandma cockblock if ii ever heard of it
by Shapreston July 21, 2010