A garboon is a more specific racist term than words such as "nigger" or "coon". It refers to large black men (or women?) with particularly stereotypically "black" features, the likes of which would be found in a racist portrayal, e.g. enormous lips, wide and flat nose, extreme prognathism. Possible etymologies include the word "baboon" and "Gabon" (an African country) and the fact that the word sounds like some species of ape.
Did you see that garboon with the horizontal vagina of a mouth on his face?
An ashtray stand. Commonly found in public spaces or semi public spaces as a courtesy to patrons. The top of which is filled with a shallow layer of sand in a tray used to extinguish tobacco butts. Also found within the sand, gum, spit, boogers, matches and other small useless items found at the bottom of trouser pockets.
Father and son are waiting to get hair cut. Son is sitting next to a garboon and begins to play in the sand with his fingers. Father looks at son with disgust and retorts,