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.

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.

3. (Mach.) A kind of hydraulic brake for regulating the action of pumping engines and other machines; -- sometimes called dashpot.

Source: Webster's Revised Unabridged Dictionary (1913)