3Bet

1. The act of making a raise against a raise in a hand, or in other words, the final bet in the sequence of Big Blind - Raise - 3Bet.

Explained

A 3Bet occurs when a player raises the original raiser in a hand. For example:

Small & Big Blind Post for $1 and $2 respectively.
1. "Player A" in mid position makes a raise to $7.
2. "Player B" on the button makes another raise (the "3Bet") to $22.

Ranges

Years ago, it was said that only "young internet no limit" players made 3Bets but due to the heightened aggression in games, 3bets are now common place in limit and no limit games. Typically in Full Ring play 3Bet ranges will be from 4-6% for the average player while a 6-handed game will see the average player have a range of 5-9%. 3Bets are used, typically, to exploit a positional advantage in the hand.