Usually used in context of a video game: To either accidentally or on purpose push or deflect another player, causing them to fall off a ledge or platform, miss an intended objective, or fail in any other way. Popularized by Gavin Free of Achievement Hunter.
Ohhh, sausages! I would've made that jump, only Ryan bunced me just as I was about to land!
Dude1: Hey buddy, great shades!
Dude2: Thanks dude, and just 50 bunce from a random guy in the pub
Dude1: 50 bunce!! You've been frikkin ripped there bud
Dude2: No way, he assured me they are genuine fakes
A person of incredibly low intelligence; generally unable to spell their own name, unable to perform simple tasks, and incapable of voluntary breathing.