n. One who has the authority or power to command or order; especially, a military leader; the chief officer of an army or of any division of it.n. Hence One who has control, in any sense.n. Specifically In the British and United States navies, an officer next in rank below a captain and above a lieutenant or a lieutenant-commander.n. The chief officer of a commandery in the medieval orders of Knights Hospitallers, Templars, etc. See commandery, 2 .n. A similar officer in certain secret orders, as in the American order of Knights Templars.n. A member of a higher class in a modern honorary order.n. A heavy beetle or wooden mallet used in paving, or by sailmakers and riggers.n. In surgery, a box or cradle for incasing an injured limb.n. In hat-making, a string which is pressed down over a conical hat while it is on the block, to bring it to the required cylindrical form.n. In medieval fortification, same as cavalier, 5.n. A member of the highest class, or one of the highest classes, of some modern honorary orders. See order. Synonyms Leader, Head, etc. See chief.