one who has no teeth. a prostitute or whore. real sketchy in apearance. a mess, or messy. slutty, possibly having std's or full bore AIDS.
friend: YOA NAG! look at this greasy bitch havin a dart.
me: yikes, quite the gummer
friend: wow this chick smells like fish.
other friend: must be some sort of bottom feeder.
me: ya man, shes gummi'n