In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves.
but the same waves could be reproduced without gravity in an appropriate accelerating frame (e.g. in a rotating body at a Lagrange point) so gravity isn't _essential_, whereas it is for gravitational waves
From the first paragraph of the wiki-page:
In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves.