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Add-on
1. The option to purchase an additional and specified amount of chips at a particular time mid-tournament. Unlike re-buys, this option is granted to all remaining players regardless of stack size.
"I prefer tournaments with an add-on since I can get a chance to play before I decide whether or not I am willing to risk some extra money."

2. The amount of money required and amount of chips received if a player chooses to purchase more chips.
"The add-on was $80 for another 800 chips."

3. In a tournament, to purchase additional chips at the end of the re-buy period; to purchase an add-on.
"I'll add on."

4. The point in time at which the re-buy period ends and players have the option to purchase a specific amount of additional chips.
"A number of the maniacs in the earlier stages of the tournament started to play more conservatively after the add-on."

5. Outside of tournament games, to purchase additional chips prior to losing all of the chips with which one began; to purchase an add-on.
"I bought in for $90 but was down to $20 by the end of two hours. I decided to add-on $40 and go home if I got down to the felt or won enough to at least break even."
 
Australian Poker Weekly