of speculum-a mirror, or looking-glass; especially, a metal mirror, as in greek and roman archaeology.-a reflector of polished metal, especially one used in reflecting telescopes. see speculum metal, below.-an instrument for dilating certain passages of the body, and throwing light within them, thus facilitating examination or surgical operations.-a bright and lustrous patch of color found on the wings of ducks and some other birds. it is usually situated on the distal portions of the secondary quills, and is much more brilliant in the adult male than in the female.