Prankster (ability)

Effect

Prankster increases the priority of status moves by +1.

This means that a slower Pokémon with Prankster can use a status move before the opponent uses a regular move. Or if the ability-bearer is faster, it could use a status move before the opponent uses a priority move like Aqua Jet.

The move Quick Guard does not block moves whose priority is increased by Prankster (but it does block moves that already have increased priority).

Game descriptions

Pokémon with Prankster

Prankster as a hidden ability