- (idiomatic) To outdo, to do something slightly better than a competitor's prior effort.
- Every year the neighbors try to one-up each other with their holiday lights.
- "Time flies when you're having fun!" said one of the skiers in our party. "Yeah, but time's more fun when you're flying," Jay one-upped.
do something slightly better than a competitor
- (especially in phrases like get one up on someone) An advantage over someone.
- WePay wants to get one-up in the mobile payments race with its new iOS app for small businesses.
- (video games) An additional life or object that gives the player an extra chance to play.
- If you hit that block, you can get a one up.
In the video games context, almost always written 1UP.