A facility, comparable to a wind tunnel, in which an underwater component may be tested in a controlled flow of water. / A tunnel used to transport water.

The removal of calcium and magnesium ions from water, or their replacement with sodium, either by chemical reaction or by ion exchange.

contamination of water, especially surface water, by sewage effluent, fertilizer runoff, industrial chemical discharge etc.

A potentially fatal medical condition, also called water intoxication, caused by extremely rapid intake of water. / Contaminating a water source with a toxin.

ocean dumping

A potentially fatal disturbance in brain function that results when the normal balance of electrolytes in the body is pushed outside of safe limits by a very rapid intake of water.

Alternative spelling of freshwater

The dirty water which is left over after one mops. / (figuratively) Any liquid which is reminiscent of such dirty water.

Non-Oxford British English standard spelling of water of crystallization.

Any water-based cyclone, usually much smaller than a tornado in magnitude.