When you buy more chips before you leave the game. Re-buys are permitted in some tournaments for players who fall below a certain point. The time during which one may re-buy is called the "re-buy period". Tournaments with re-buys are called "re-buy tournaments".
If you run out of chips in a tournament, and you wish to continue playing, you then re-buy, meaning, you buy more chips. This is only legal in re-buy tournaments. You can only re-buy up until a certain point. See also: ADD-ON.
a second (or third, or fourth) chance for a player eliminated from a tournament to buy more chips to remain in the game. The “re-buy period”, often characterised by extremely loose and aggressive play, is the predetermined time at the beginning of a tournament where re-buys are permitted. See “freeze-out
When poker tournaments allow players to buy more chips after the start, those chips purchases are called re-buys. They will only be allowed for a set amount of time. A poker tournament without re-buys is called a freeze out.