Slow is a Magic Command found in Kingdom Hearts Birth by Sleep. It slows down the movements and attacks of enemies within a certain radius.
Origin
The Magic Slow originated in the Final Fantasy Series to allow the player to get in more hits before the enemy. It's counter part is Haste.
Trivia
Kingdom Hearts 358/2 Days Featured Haste as an ability. But not Slow. Kingdom Hearts Birth by sleep Is the only Kingdom Hearts Title to feature slow. Every other Title so far only showcases the magic Stop.