the act of staring one down, mainly directly in the eyes. not neccessarily bad or good. usually if you grill the opposite sex, it implies an interest in them, and if heterosexuals grill the same gender, it usually means they dont like them, are testing them, and wouldnt mind smacking the sh-t outa them.
> good: "hey buck, that girl is GRILLIN you HARDCORE, go talk to her"
> bad: "if that punk dont stop grillin, im'a see if he got a problem"