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!
3. slang An initialism of "overpowered," referring to a character, weapon, move, or other aspect of the game that is unfairly strong in comparison to the rest of the game. Beating the side quest nets you a mystical sword that is so OP that you basically can't be beaten from that point on. The new character they added to the fighting game has a very cool design, but she is totally OP. Unless the developers nerf her moves, I doubt she'll be allowed in competitive play.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.


n. other people’s cigarettes; begged or borrowed cigarettes. (Initialism.) My favorite kind of cigarettes is OP’s. They’re the cheapest, too.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.