speculum

Concise Oxford English Dictionary © 2008 Oxford University Press:
speculum /ˈspɛkjʊləm/

▶noun (pl. specula /-lə/)

• 1 Medicine a metal instrument that is used to dilate an orifice or canal in the body to allow inspection.

• 2 Ornithology a bright patch of plumage on the wings of certain birds, especially ducks.

• 3 a mirror or reflector, especially (formerly) a metallic mirror in a reflecting telescope. ■short for speculum metal.

– origin ME: from L., lit. ‘mirror’, from specere ‘to look’.