A postilion is a person who rides the (leading) nearside (left-hand side) horse drawing a coach or carriage, esp. when one pair only is used and there is no coachman. Also in extended use: an outrider for a carriage. A postilion can also be a guide or forerunner for the post, or for a messenger. It can also refer to a person who rides a post-horse, or to a courier or a swift messenger.