Half-inch is an ability in Dragon Quest IX learned by allocating 10 skill points into the Thief's acquisitiveness. When used, the user attempts to steal an item from the enemy, with the sucess rate corresponding to the user's deftness. The stolen item is added to the character's inventory. This skill costs no MP to use, and although a character cannot steal more than one item from the same monster, the monster still has the normal random chance drops.
The term Half-inch is British slang for 'steal'.