Green’s Dictionary of Slang

curbie n.

(US juv.) lit. a student who smokes between classes on the curb outside the school; thus ext. to mean any school rebel.

OnLine Dict. of Playground Sl. 🌐 curbie n. Used to describe high-school students who smoke cigarettes between classes. Smoking is not allowed on most high school campuses, so students who smoke go across the street and sit on the curb to smoke. Sometimes more than tobacco is smoked. Word generally describes kids in the ‘tough croud’ [sic] who wear all black and rebel against authority any chance they get.