spec·u·lum / ˈspekyələm/ • n. (pl. -la / -lə/ ) 1. Med. a metal or plastic instrument that is used to dilate an orifice or canal in the body to allow inspection.2. Ornithol. a bright patch of plumage on the wings of certain birds, esp. a strip of metallic sheen on the secondary flight feathers of many ducks.3. a mirror or reflector of glass or metal, esp. (formerly) a metallic mirror in a reflecting telescope. ∎ short for speculum metal.

speculum (spek-yoo-lŭm) n. (pl. specula) a metal instrument for inserting into and holding open a cavity of the body, such as the vagina, rectum, or nasal orifice, in order that the interior may be examined.

speculum In birds, a well-defined patch of coloured feathers, often iridescent, found on the secondaries or secondary coverts (e.g. of many Anatidae, particularly Anas species).

Speculum

The crystal ball or any shining, light-refracting surface that a scryer uses for divination, i.e., crystal gazing.