The Bomb is a Pickup that activates automatically once auto-selected (expect when using SADIST cheat). Upon activation, the car turns black and its antenna starts burning down like a fuse. After ten seconds, when the fuse reaches the bottom, the car blows up.
While a bomb can't be defused, the player can pass it off to other racers by touching them. The victim gains the remaining fuse time.
In Re-Volt 1.2 or RVGL, hitting a Clone Pick Up while in fuse time, the car will explode imediately, discarding the remaining time. It's not the same in the legacy versions, where the fuse keeps going even collecting a false pickup.