From the Kingdom Hearts Wiki: A world of information not accessible by Gummiship
Swordbill (エアパッシング, Ea Passhingu?, lit. "Air Passing") is a technique that appears in Kingdom Hearts Birth by Sleep. It allows the user to perform a speedy flurry of jabs at an enemy, then perform a finishing stab.
Swordbill is a Finish command. Pressing repeatedly increases the speed of the attack.
Kingdom Hearts Birth by Sleep