n. (pl. specula) 1 Surgery an instrument for dilating the cavities of the human body for inspection. 2 a mirror, usu. of polished metal, esp. in a reflecting telescope. 3 Ornithol. a lustrous coloured area on the wing of some birds, esp. ducks. speculum-metal an alloy of copper and tin used as a mirror, esp. in a telescope.
[ L, = mirror, f. specere look ]