This means a special one time opportunity to buy more chips in the middle of a poker game. In a poker game a player adds on chips just before he is running out of. In a poker tournament, after the re-buy period is done, each player is entitled for (usually one) add-on, no matter how many chips he has. Usually in an add-no there is no minimum chips obligation and you get more chips than in the rebuys. Example: This poker tournament is going for 60$ buy-ins, unlimited rebuys for the first three levels, plus an optional add-on after the rebuy period.