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a descent of water over a steep surface; a waterfall, especially one of considerable size.
any furious rush or downpour of water; deluge.
Ophthalmology.

an abnormality of the eye, characterized by opacity of the lens.
the opaque area.

Historical Examples

No other eye disease and no prevalent constitutional diseases or degeneracies in the cataractous stock.
Abstracts of Papers Read at the First International Eugenics Congress Various

noun
a large waterfall or rapids
a deluge; downpour
(pathol)

partial or total opacity of the crystalline lens of the eye
the opaque area

n.

early 15c., “a waterfall, floodgate,” from Latin cataracta “waterfall,” from Greek katarhaktes “waterfall, broken water; a kind of portcullis,” noun use of an adjective compound meaning “swooping, down-rushing,” from kata “down” (see cata-). The second element is traced either to arhattein “to strike hard” (in which case the compound is kat-arrhattein), or to rhattein “to dash, break.”

Its alternative sense in Latin of “portcullis” probably was passed through French to form the English meaning “eye disease” (early 15c.), on the notion of “obstruction” (to eyesight).

cataract cat·a·ract (kāt’ə-rākt’)
n.
Opacity of the lens or capsule of the eye, causing impairment of vision or blindness.
cat’a·rac’tous (-rāk’təs) adj.
cataract
(kāt’ə-rākt’)

An opacity of the lens of the eye or the membrane that covers it, causing impairment of vision or blindness.

A waterfall in which a large volume of water flows over a steep precipice.

cataract [(kat-uh-rakt)]

A loss in the transparency of the lens of the eye, which reduces a person’s ability to see. The condition can be treated by surgically removing the lens and replacing it with an artificial one, or with corrective eyeglasses or contact lenses.