WATERSPOUT

n. pipe for rainwater; tornado over water

A waterspout is an intense columnar vortex (usually appearing as a funnel-shaped cloud) that occurs over a body of water and is connected to a cumuliform cloud. In the common form, it is a nonsupercell tornado over water, and brings the water upward. Also, it is weaker than most of its land counterparts.
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Noun
1. a tornado passing over water and picking up a column of water and mist
(hypernym) tornado, twister
2. a heavy rain
(synonym) downpour, cloudburst, deluge, torrent, pelter, soaker
(hypernym) rain, rainfall
3. a channel through which water is discharged (especially one used for drainage from the gutters of a roof)
(hypernym) conduit

(n.)
A remarkable meteorological phenomenon, of the nature of a tornado or whirlwind, usually observed over the sea, but sometimes over the land.
  

In general, a tornado occurring over water. Specifically, it normally refers to a small, relatively weak rotating column of air over water beneath a Cb or towering cumulus cloud. Waterspouts are most common over tropical or subtropical waters.
The exact definition of waterspout is debatable. In most cases the term is reserved for small vortices over water that are not associated with storm-scale rotation (i.e., they are the water-based equivalent of landspouts ). But there is sufficient justification for calling virtually any rotating column of air a waterspout if it is in contact with a water surface.