O&O Stations (owned and operated) – A station owned and operated by a network.  For example, NBC owns and operates both WRC Radio and WRC-TV.

Open Line Rate – Cost of agate line in newspaper run once.

Opt In – A process where by a user voluntarily agrees to start receiving email, usually commercial, about a topic of interest.

Opt Out – A process where by a user voluntarily agrees to stop receiving email, usually commercial, about a topic of interest.

Orbit – A strategy used by (television) stations to rotate prime time spots over a specific period of time.  For instance, if a buyer wanted to run in three prime time programs over the course of three weeks, program #1 could run in week #3, program #2 could run in week #2, and program #3 could run in week #1. Gives the station flexibility to shift prime spots around to their advantage.

OTO (one time only) – A spot that is to run only once.

Overnights – A service provided by Neilsen which reports audiences watching prime time programs the day after the broadcast.