Cut from the AirSource Weapon Master's Handbook pg. 22
Your powerful and swift attacks can slice ranged attacks out of the air.
Prerequisites: Str 13, Power Attack, base attack bonus +5, weapon training class feature with a melee weapon.
Benefit: When a ranged attack is made against you or a target adjacent to you, you can cut the weapon (or ammunition) out of the air, deflecting the attack so the target takes no damage. As an attack of opportunity, make a melee attack roll at your highest bonus. If the result is greater than the attack roll total of the ranged attack, the attack is deflected. You must be aware of the attack and not flat-footed. Unusually massive ranged weapons (such as boulders or ballista bolts) and ranged attacks generated by spell effects cannot be deflected.