1. slang An initialism for "other people," referring to a cigarette given to one by someone whom one asked for it. He stumbled out of the bar going around to the people outside looking for OPs.
2. slang By extension, a person who asks someone for a cigarette. Cynthia doesn't smoke for the most part, but whenever we go out drinking she turns into such an OP!
n. other people’s cigarettes; begged or borrowed cigarettes. (Initialism.) My favorite kind of cigarettes is OP’s. They’re the cheapest, too.