The Collaborative International Dictionary of English v.0.48:

Monocle \Mon"o*cle\, n. [F. See Monocular.]
   An eyeglass for one eye. --Simmonds.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Eyeglass \Eye"glass`\, n.
   1. A lens of glass worn in front of the eye to assist vision;
      -- usually used in the plural, referring to a pair of
      lenses fixed together in a frame, and worn resting on the
      bridge of the nose, to improve the vision. A single
      eyeglass in a frame is called a monocle.
      [1913 Webster +PJC]

   2. Eyepiece of a telescope, microscope, etc.
      [1913 Webster]

   3. The retina. [Poetic]
      [1913 Webster]

   4. A glass eyecup. See Eyecup.
      [1913 Webster]

WordNet (r) 3.0 (2006):

monocle
    n 1: lens for correcting defective vision in one eye; held in
         place by facial muscles [syn: monocle, eyeglass]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "monocle":
   Polaroid glasses, bifocals, blinkers, cheaters, colored glasses,
   contact lens, dark glasses, divided spectacles, eyeglass,
   eyeglasses, glasses, goggles, granny glasses, harlequin glasses,
   horn-rimmed glasses, lorgnette, lorgnon, mini-specs, nippers,
   pair of glasses, peepers, quizzing glass, readers, reading glasses,
   shades, specs, spectacles, sun-specs, sunglasses, trifocals