Definition of squeeze play
A squeeze is when a player 3bet when there is already an open raise and a cold call. The most common squeeze play is when the player on the open raise button, the player on the small blind call and the player on the big blind 3bet. His 3bet will be named "squeeze play". Generally, it is more strategic to do a squeeze play in position, but the squeeze play out of position can also be an option.
Why do we do a squeeze play?
The player who squeeze wants to have the initiative. He doesn't want to simply call out of position and be bluffed by the player in position who may represent a range of hands. The player who squeeze in BB position when the button opens and the player in SB call position does so because the button has a big range and will have to fold often. The same is true for the small blind. If the player in the SB position had a big hand, he probably would have made a 3bet. The 3bet will have a high success rate here. And when the player who makes a squeeze play is called, he can still represent a wide range of hands and win the hand after the flop.