The act of rolling one's penis in Grape flavoured Kool-Aid powder and then inserting it in the girl's (or guy's) mouth. The moisture of their mouth mixes with the Kool-Aid powder creating a delightful grape flavoured drink in their mouth. Graping is most popular among people in the Ghetto as they generally like "Pawrpull Drank" and don't use/are too poor to afford flavoured condoms.
Hey G, I just handcuffed your mom to the radiator and graped her in the mouth. Then I went to the basement and graped 4 of your sisters.