In poker, “acting out of turn” means making a betting decision before it is your turn to act. This can include any action that is taken out of turn, such as checking, betting, calling, raising, or folding.
Acting out of turn can be a serious breach of poker etiquette, as it can give an unfair advantage to the player who acts out of turn. It can also affect the dynamics of the hand and give other players information they would not have had otherwise, potentially changing the course of the hand.
If a player acts out of turn, the dealer will generally ask them to wait until it is their turn to act and revert the action that they took out of turn. Depending on the severity of the infraction, a player who acts out of turn may receive a warning, a penalty, or be forced to sit out of the hand altogether.