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1. Grinfuck
From the song, Grinfucked on The Fury of Our Maker's Hand by Devil Driver. Meaning to screw someone over all the while they believe you are their friend.
The way your boss took the credit for your work all the while telling you that he was going put you up for promotion. You just got grinfucked hard.
2. Grinfuck
The act of slitting somebodies mouth open from side to side (IE chelsea smile) And then repeatedly fucking the gaping wound.
When I grinfucked Tom.
3. Grinfuck
The act of making a "WHOO" sound really loud and its sorta like a death metal growl.
"Hey grinfuck that guy!"

-innocent guy walks by-

"WHOO!!"

-guy gets scared runs away"
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