A mirror, or looking-glass; especially, a metal mirror, as in Greek and Roman archæology.
- A mirror or polished metal plate used as a reflector in optical instruments.
- An instrument for dilating the opening of a body cavity for medical examination.
- Zoology A bright, often iridescent patch of color on the wings of certain birds, especially ducks.
- Zoology A transparent spot in the wings of some butterflies or moths.