(Trip is a special maneuver)
You can attempt to trip an opponent as a standard action. You may use either your maneuver bonus or your attack bonus with the weapon you are using (if any) to make a trip attempt. If your attempt is successful, the target is knocked prone. If your attempt fails by 10 or more, you are knocked prone instead. If the target has more than two legs, add +2 to the Difficulty of the combat maneuver roll for each additional leg it has. Some creatures, such as oozes without legs and flying creatures, cannot be tripped.