catopter

noun3

1. •
   A unit of measure of the converging power of a curved mirror, equal to the reciprocal of the focal length in meters; a diopter applied to a curved reflective surface as opposed to a lens.

   • This focus divided into 40", gives the catopters. — 1916
2. •
   An Ancient Greek anal dilator or speculum.

   • Hippocrates (B.C. 432) described an instrument, the catopter, which was undoubtedly used as an anal speculum, — 1897
3. •
   (no longer used) A reflecting optical glass or instrument; a mirror.

   • My Cat whose black fur was so glossy and fine Her use of Catharon one well could divine. Almost indeed a Catopter she showed. — 1885