An Etymological Dictionary of Astronomy and Astrophysics

1. A wave that forms and propagates at the free → surface of a body of → fluid after that surface has been disturbed and the fluid particles have been displaced from their original positions. The motion of such waves is controlled by the restoring force of gravity rather than by the surface tension of the fluid.
   

2. Not to be confounded with → gravitational wave.

See also: → gravity; → wave.