When a girl is sucking a guys cock, the guys hits her over the head with a baseball bat and knocks her out.
Bro, I fucking grand slammed ur mom last night
by Freye December 08, 2008
when a guy cums on some ones face and then slams his penis across their face
man i grand slam that bitch the other day
by lui rodriguez May 14, 2007
During intercourse, one takes out a baseball bat and rams it into the anus, ad=nd when the bitch screams, take it out and knock her ass out.
I gave my grandma the grand slam yesterday.
by billy bob February 05, 2003
Term is used to describe the event of when you wake up with major morning wood the size of a Denny's plate full of breakfast awesomeness.
Eric: I woke up on my girlfriend's mom's couch to her whole family staring at my grand slam! Needless to say, they were quite impressed.
by RiddyTX June 17, 2015
When four or more of your friends hook up with the same girl at different times. Can only be completed if each person goes all the way (i.e. hitting a home run).
Dude, me, Bobby, Ned, and Tom hit a Grand Slam with Jennie.
by YaMumz September 10, 2014