Merriam-Webster Collegiate Dictionary - speculum

 noun  (plural specula; also -lums)  Etymology: Middle English, from Latin, mirror, from specere  Date: 15th century  1. an instrument inserted into a body passage especially to facilitate visual inspection or medication  2. a drawing or table showing the relative positions of all the planets (as in an astrological nativity)  3. a patch of color on the secondaries of most ducks and some other birds