If a character is dangling from the ground off their feet while they're held in a grab, they will break free from the grab in what is called a Jump Break, where they jump into the air to break free. This will only happen if the player grabbing the character does not jab holding them before they're about to break free.
Certain characters have a laggy Jump Break that leaves them vulnerable for the time they break, and this can be abused by following it up with certain attacks. Marth is fairly tall, so he can use this well since he will make a lot of characters dangle off the ground due to his height.
This is useful on characters like Meta Knight, Wario, G&W, and et cetera. Go to my thread in my siggy for a full list of who can be hit and how.
