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noun cat·a·ract \ˈka-tə-ˌrakt\

Simple Definition of cataract

  • medical : a condition in which a part of your eye (called the lens) becomes cloudy and you cannot see well

  • : a large waterfall

Source: Merriam-Webster's Learner's Dictionary

Full Definition of cataract

  1. 1 [Middle English, from Middle French or Medieval Latin; Middle French catharacte, from Medieval Latin cataracta, from Latin, portcullis] :  a clouding of the lens of the eye or of its surrounding transparent membrane that obstructs the passage of light

  2. 2 a obsolete :  waterspout b :  waterfall; especially :  a large one over a precipice c :  steep rapids in a river d :  downpour, flood <cataracts of rain> <cataracts of information>

cataractous play \ˌka-tə-ˈrak-təs\ adjective

Examples of cataract in a sentence

  1. <the roaring cataract is one of the park's most majestic sights>

  2. <in spring the melting snows usually produce a cataract that inundates the valley>

Did You Know?

The meaning of "cataract" we're most familiar with is also the oldest. It dates to the 14th century and comes from the Latin word cataracta, meaning "portcullis," probably because the ocular cataract obstructs vision in a way reminiscent of the way the portcullis's heavy iron grating obstructs passage into a fortress or castle. Latin cataracta has another meaning, however-"waterfall"-and that meaning gave us the water-related meanings that came in later centuries. The connection between the two Latin meanings can be seen in katarassein, the Greek source of cataracta. It means "to dash down"-an action we see in both the slamming portcullis and the cascading waterfall.

Origin of cataract

Latin cataracta waterfall, portcullis, from Greek kataraktēs, from katarassein to dash down, from kata- + arassein to strike, dash

First Known Use: 14th century

CATARACT Defined for Kids


noun cat·a·ract \ˈka-tə-ˌrakt\

Definition of cataract for Students

  1. 1 :  a clouding of the lens of the eye or of the cover around the lens that blocks the passage of light

  2. 2 :  a large waterfall

  3. 3 :  a sudden rush or flow like a waterfall

Medical Dictionary


noun cat·a·ract \ˈkat-ə-ˌrakt\

Medical Definition of cataract

  1. :  a clouding of the lens of the eye or its surrounding transparent membrane that obstructs the passage of light

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