cat·a·ract (k?t??-r?kt?)n.1. A large or high waterfall.2. A great downpour; a deluge.3. Medicine Opacity of the lens or capsule of the eye, causing impairment of vision or blindness.[Middle English cataracte, from Old French, from Latin cataracta, from Greek katarrakt?s, katarakt?s, downrush, waterfall, portcullis, probably from katarassein, to dash down (kat-, kata-, cata- + arassein, to strike). Sense 3, from a comparison to a portcullis or other falling impediment or covering.]cat?a·rac?tous (-r?k?t?s) adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.cataract (?kæt??rækt) n1. (Physical Geography) a large waterfall or rapids2. a deluge; downpour3. (Pathology) pathol a. partial or total opacity of the crystalline lens of the eyeb. the opaque area[C15: from Latin catarracta, from Greek katarrhakt?s, from katarassein to dash down, from arassein to strike]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014cat?a?ract (?kæt ??rækt) n. 1. a descent of water over a steep surface; a waterfall, esp. one of considerable size. 2. any furious rush or downpour of water; deluge. 3. a. an abnormality of the eye characterized by opacity of the lens. b. the opaque area. [1350?1400; Middle English