From the Super Mario Wiki
Mud Slinger! is the name of Petey Piranha's Super Ability, executed in Mario Strikers Charged. Petey Piranha must first earn his special item, symbolized as his head. Once this is collected, Petey will be able to puke large amounts of mud onto the ground. This greatly lowers the speed of every player and item, except for Petey himself. He can use this Super Ability at least four times in one move, and the amount of times he has used it is shown on a meter on the top of the screen. This move is one of the most useful Super Abilities in the game.