Cavalier, in English history, one of the supporters of Charles I in the English Civil War that began in 1642. The Cavaliers, or Royalists, opposed the Parliamentarians, who were called Roundheads because most of them wore their hair cropped close to their heads. Cavalier, originally a term for an armed horseman, had come to mean a high-spirited military man or gallant. The Parliamentarians, most of whom were Puritans, applied the term to the Royalists in disapproval of their dress and hairstyle, which the Puritans thought too frivolous. When the Cavaliers gained power in 1660, they took the name as a title of honor. The first parliament of Charles II, 1661--79, was called the Cavalier Parliament. In 1679, Cavaliers began to be called Tories.