noun: A mythical figure who has appeared in folklore around the world since the Middle Ages, who is traditionally depicted as a man upon horseback who is missing his head.
noun: A mythical man (perhaps of several) upon horseback who is missing his head, inspired by the Headless Horseman mythical figure.
noun: (slang) A corpse of a man that is missing the head due to decapitation.
noun: Alternative letter-case form of Headless Horseman [A mythical figure who has appeared in folklore around the world since the Middle Ages, who is traditionally depicted as a man upon horseback who is missing his head.]