*Gravity waves* are a term of art used by people who study wave behavior in liquids in which gravity and a free surface are present. Gravity waves in water are the large, fast-moving ones stirred up by strong winds, that surfers ride on and that can crash over and capsize large ships at sea. In this special context, they have nothing to do with waves in the fabric of spacetime. 

(The other type of waves in water are *capillary waves*, in which the restoring force that strives to smooth them out is not gravity but *surface tension*. These are tiny waves that move slowly, and are produced by things like wiggling insects floating on the surface of the water.)