When a slut is really bad at giving head and uses her teeth instead of her lips. The name is given because her teeth on your dick was like taking your dick to a cheese grater. Often result in blue balls or just well you know...
guy coming out of bed room: *look of pain on face*
a bro: "dude you don't look to good what happened in there?"
gcobr: "it was horrible she was horrible" *sigh*
a bro: "ohhhhh she grated you dick didn't she?"
gcobr: "bro yea I think I need ice or like a massage"
girl giving head for the first time (has no idea what she's doing)
bro receiving it: "ahhh careful with you teeth"
girl: "oh sorry what"
bro: "yea if you keep that up I'll end up with a grated dick"