(n.) A girl who is especially pretty, funny, and SO smart. She often laughs at her own (hilarious) jokes, and can be spotted wearing a thick, white headband much of the time. In addition, all the boys want a katyboat of their own, but not every boy gets one. A katyboat is always very picky about her boys.
Joe: "I can't believe how smart that katyboat is! She got a 92 on her engineering physics test! I only got a 70. That white headband is probably good luck. She'd never like me... I'm too stupid for her!"
Kelly - "No duh."