You make a single attack that deals significantly more damage than normal.
Prerequisites
Base attack bonus +6.
Benefit
Once per round, when you make an attack action, you can make it deal additional damage. Roll the weapon’s damage dice for the attack twice and add the results together before adding bonuses from Strength, weapon abilities (such as flaming), precision-based damage, and other damage bonuses. These extra weapon damage dice are not multiplied on a critical hit or from potency bonuses, but are added to the total and maximized.
If your base attack bonus is +11 or higher, you roll weapon’s damage dice for the attack three times instead of twice.
If your base attack bonus is +16 or higher, you roll weapon’s damage dice for the attack four times instead of three times.
A vital strike attack is still considered to be an attack action for any effects that modify attack actions.