A celebratory exclamation, usually delivered with a
squeaky or high-pitched
intonation.
The last word--capowie--can never be spelled
with a K. Ever. That would just be silly.
Larry: Oh my
god!
Leslie: What is it, Larry?
Larry: I just got a new high score in Robot
Unicorn Attack!
Leslie: YEAHYEAHYEAH WOWIE CAPOWIE!