Rough Skin is an ability introduced in Generation 3.
In battle Edit
When a Pokémon with this Ability is hit by a move that makes contact, the attacking Pokémon loses 1/8 of its own maximum HP.
If a Pokémon with this Ability is hit by a multi-strike move that makes contact (such as Fury Swipes), each hit will activate this Ability.
Outside of battle Edit
Rough Skin has no effect outside of battle.