Noun
a broad and deep undulation of the ocean
an obvious change of public opinion or political sentiment that occurs without leadership or overt expression
Source: WordNetThe ground swell is what's going to sink you as well as being what buoys you up. These are cliches also, of course, and I'm sometimes interested in how much one can get away with. Paul Muldoon
there was a ground swell of antiwar sentiment Source: Internet