Noun. A plastic bag (usually from a grocery store, bodega or other ghetto-mart) that has been inflated and borne aloft by the wind, giving it a jellyfish like appearance. Common in neighborhoods where littering is acceptable but walking on a sidewalk isn't.
I almost ran over that ho because she stepped out infront of me right as an urban jellyfish splatted up against my windshield.
A used condom discarded within an urban setting such as a busy street or project courtyard.
Ahhh shit, the other day I slipped on an urban jellyfish lying on my stoop and almost wrecked my new dunks. Then later I seen my two pit-bulls playing tug-o-war with the same jellyfish and it snapped, the jiz was all over their face.
Small (or large) patches of spittle on the pavement.
Careful baby, don't step on that urban jellyfish, you don't know where it's been.