A small piece of marble, glass, earthenware, or the like,
   having a square, or nearly square, face, used by the ancients for
   mosaic, as for making pavements, for ornamenting walls, and like
   purposes; also, a similar piece of ivory, bone, wood, etc., used as a
   ticket of admission to theaters, or as a certificate for successful
   gladiators, and as a token for various other purposes.