koom Share definition Flag v. n. adj. adv. meaning to suck it. Usually accompanied by swift hand motions resembling karate chops to the crotch (the classic suck it hand/body motion). Ho 1: "Oh em gee, J-Mama, you are such a biotch!" Ho 2: "Just koom." koom by McKoominitt January 11, 2009 Get the koom mug.