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

Moby Thesaurus II by Grady Ward, 1.0:

146 Moby Thesaurus words for "cataract":
   Niagara, ablepsia, amaurosis, benightedness, blepharitis,
   blind side, blind spot, blindfolding, blinding, blindness,
   blurring the eyes, cascade, cataclysm, cecity, choroiditis, chute,
   collapse, come down, comedown, conjunctivitis, crash, cross-eye,
   darkness, debacle, declension, declination, defective vision,
   defluxion, deluge, depriving of sight, descend, descending,
   descension, descent, detached retina, dim-sightedness, dip down,
   down, downbend, downcome, downcurve, downfall, downflow, downgrade,
   downpour, downrush, downtrend, downturn, downward trend, drop,
   drop down, drop off, drop serene, dropping, economic blindness,
   engulf, esotropia, ever-during dark, excecation, eye defect,
   eyelessness, fall, fall down, fall off, falling, falls, flood,
   flooding, force, fresh, freshet, glaucoma, go down, go downhill,
   gravitate, gravitation, gutta serena, hoodwinking, inclination,
   inundate, inundation, iritis, keratitis, lack of vision, linn,
   lose altitude, making blind, nappe, niphablepsia, optic neuritis,
   overbrim, overflow, overrun, overwhelm, parachute,
   partial blindness, pink eye, pitch, plummet, plummeting, plunge,
   pounce, pour, pour down, pour out, pour over, precipitate,
   psychic blindness, rain, rapids, reduced sight, retinoblastoma,
   river, run over, sault, sightless eyes, sightlessness, slop, slosh,
   snow blindness, soul-blindness, spate, spill, spill out,
   spill over, spiritual blindness, spout, stone-blindness, stoop,
   sty, submerge, swamp, sweep, swoop, torrent, total blindness,
   trachoma, trend downward, unenlightenment, unseeingness, uveitis,
   walleye, waterfall, waterflood, watershoot, whelm