A facial wound where the victim's mouth is slit from the corners, giving the impression of a wide, yet forced smile.
Also known as "Chelsea smile".
Notable examples
Kuchisake-onna, ("Slit-Mouthed Woman") The tale of a woman, mutilated by a jealous husband, and returned as a malevolent spirit. Her defining characteristic is her mouth, which extends from ear to ear in a horrible, permanent smile.