In the field of Geophysical Fluid Dynamics it is an important distinction as there are other very important waves. Rossby waves are not gravity waves and extremely important to the global climate (see their role in ENSO dynamics). Compressive waves (acoustic waves) are everywhere of course. There are also topographic Rossby waves, internal waves and Kelvin waves (note: kelvin waves and internal waves are gravity waves as well). Oh, and inertial waves!
Hubble just spotted a "bullseye" galaxy where a smaller galaxy passed through the center and caused ripples in the gas bobbing with gravity, like dropping a stone in a pond:
This, in three(plus one) dimensions and with some devilish complication, is what I imagine quantum relativity (theory of everything) will turn out to be — elementary particles as topological structures made of spacetime. String theory seems to have gone astray in the name of feasible computability/somewhat comprehensible mathematical structure.
> Compared to similar experiments with solid targets, the water sheet reduced the proton beam's divergence by an order of magnitude and increased the beam's efficiency by a factor of 100.
https://en.m.wikipedia.org/wiki/Gravity_wave