Merriam-Webster Collegiate Dictionary - cataract

 noun  Etymology: Latin ~a waterfall, portcullis, from Greek kataraktes, from katarassein to dash down, from kata- + arassein to strike, dash  Date: 14th century  1. Middle English, from Middle French or Medieval Latin; Middle French catharacte, from Medieval Latin ~a, from Latin, portcullis a clouding of the lens of the eye or of its surrounding transparent membrane that obstructs the passage of light  2.  a. obsolete waterspout  b. waterfall; especially a large one over a precipice  c. steep rapids in a river  d. downpour, flood ~s of rain ~s of information  • ~ous adjective