An item that grants the player an extra life in the game, staving off game over by one more try.
In a game with multiple players, an indicator or identifier of player 1.
(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.
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.