NOUN (2)

1. an eye disease that involves the clouding or opacification of the natural lens of the eye;

2. a large waterfall; violent rush of water over a precipice;

The Collaborative International Dictionary of English v.0.48:

Cataract \Cat"a*ract\, n. [L. cataracta, catarracles, a
   waterfall, Gr. ?, ?, fr. ? to break down; in the passive, to
   fall or rush down (of tumors) to burst; kata` down + ? to
   break.]
   1. A great fall of water over a precipice; a large waterfall.
      [1913 Webster]

   2. (Surg.) An opacity of the crystalline lens, or of its
      capsule, which prevents the passage of the rays of light
      and impairs or destroys the sight.
      [1913 Webster]

   3. (Mach.) A kind of hydraulic brake for regulating the
      action of pumping engines and other machines; -- sometimes
      called dashpot.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cataract
    n 1: an eye disease that involves the clouding or opacification
         of the natural lens of the eye
    2: a large waterfall; violent rush of water over a precipice