Definition of: speculum

(spek′yə·ləm) noun plural ·la (-lə) or ·lums
1. A mirror of polished metal or of glass coated with a metal film used for telescope reflectors and other optical instruments.
2. Med. An instrument that dilates a passage of the body for examination.
3. Ornithol. A specially colored, typically iridescent area on the wings of certain birds, as ducks. [<L, a mirror <specere see]