coin (koin)n.1. A small piece of metal, usually flat and circular, authorized by a government for use as money.2. Metal money considered as a whole.3. A flat circular piece or object felt to resemble metal money: a pizza topped with coins of pepperoni.4. A mode of expression considered standard: Two-word verbs are valid linguistic coin in the 20th century.5. Variant of quoin.tr.v. coined, coin·ing, coins 1. To make (pieces of money) from metal; mint or strike: coined silver dollars.2. To make pieces of money from (metal): coin gold.3. To devise (a new word or phrase).adj. Requiring one or more pieces of metal money for operation: a coin washing machine.Idiom: the other side of the coin One of two differing or opposing views or sides.[Middle English, from Old French, die for stamping coins, wedge, from Latin cuneus, wedge.]coin?a·ble adj.coin?er n.quoinsmooth-cut quoinsquoin also coign or coin (koin, kwoin)n.1. a. An exterior angle of a wall or other piece of masonry.b. Any of the stones used in forming such an angle, often being of large size and dressed or arranged so as to form a decorative contrast with the adjoining walls.c. A piece of wood or other material used as trim on the corner of a building in imitation of such a stone.2. A keystone.3. Printing A wedge-shaped block used to lock type in a chase.4. A wedge used to raise the level of a gun.tr.v. quoined, quoin·ing, quoins also coigned or coign·ing or coigns or coined or coin·ing or coins To provide, secure, or raise with a quoin or quoins.[Variant of coin.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.