1. an abbreviation for "K (space) Laters" or "KK (space) Laters" often followed by a comma, a series of commas, an exclamation point, and very rarely a question mark.
2. the briefest and cutest way to say farewell to a friend besides a physical kiss or a hug. sarcastically, it may be used to show great disdain, contempt, fickle weariness, or social rejection of the 'friend'
Sarah: Then why don't you go buy some?
Amy: Imma go buy those cheese fries! /waves KATERS!
Ricky: And that's me kicking your ass at Soul Calibur!
Alejandro: And that's me going home, JERK!
Alejandro: Double JERK!