Your powerful swings trade accuracy for dealing increased damage.
Prerequisites
Strength 13, base attack bonus +1.
Benefit
On your action, before making attack rolls for a round, you may choose to subtract a number from all melee attack rolls and combat maneuver checks to add the same number to all melee damage rolls. This number may not exceed your base attack bonus. The penalty on attacks and combat maneuver checks and the bonus on damage apply until your next turn.
Special
You can’t add the bonus from Power Attack to the damage dealt with a light weapon (except with unarmed strikes or natural weapon attacks), even though the penalty on attack rolls still applies.