When a Pokémon with this Ability is hit by a physical move, its Defense is decreased by one stage and its Speed is increased by one stage.
If a Pokémon with this Ability is hit by a physical multi-strike move (such as Fury Swipes), each hit activates this Ability.
Generation 7: Weak Armor now raises Speed by two stages.
Relevant Code Points
Function 0x0225708C handles all abilities which trigger when a move deals damage. This function should have a new case for Weak Armor which checks if the move is physical and then transitions to a new subscript to apply the stat changes.
Documentation
https://bulbapedia.bulbagarden.net/wiki/Weak_Armor_(Ability)
Generation 7: Weak Armor now raises Speed by two stages.
Relevant Code Points
Function
0x0225708Chandles all abilities which trigger when a move deals damage. This function should have a new case for Weak Armor which checks if the move is physical and then transitions to a new subscript to apply the stat changes.