(Disarm is a special maneuver)
You can attempt to disarm your opponent as a standard action. You may use either your maneuver bonus or your attack bonus with the weapon you are using to make a disarm attempt, against your opponent's Combat Maneuver Difficulty. If you are unarmed (possessing the Improved Strike feat counts as armed), you take a -4 penalty on your disarm attempt. Using a ranged attack to attempt a disarm likewise imposes a -4 penalty on the roll.
If your attempt is successful, your target drops one item it is carrying of your choice. If your result exceeds the Difficulty of the target by 10 or more, the target drops the items it is carrying in both hands (maximum two items if the target has more than two hands). If your result fails by 10 or more, you drop the weapon that you were using to attempt the disarm. If you successfully disarm your opponent without using a weapon, you may automatically pick up the item dropped.