A farewell greeting, generally uttered in a single syllable, used to express an urgent need to end the current conversation.
You work in a grocery store in the customer service department and are on the phone with one of your friends discussing last night's episode of America's Next Top Model, when an angry looking customer with 7 obnoxious children that make a fog horn sound like footsteps in the snow by comparison approaches.
Friend on phone: "blah blah Tyramail blah blah they had better cut Jenna NEXT time"
You: "OKBYE!" *Click*