What does "groundswell" mean?

A broad undulation of the open ocean, often as the result of a distant disturbance.

What is a synonym for "groundswell"?

Common synonyms include: inflow, mobilization, rise, surge, upsurge, upwelling.

noun

noun ·2 syllables ·Rare ·Advanced level

Noun

1
A broad undulation of the open ocean, often as the result of a distant disturbance.
2
A broadly-based shifting of public opinion. broadly
"An astonishing groundswell of support for the new Democratic frontrunner, Barack Obama, is threatening to sweep Hillary Clinton away in New Hampshire, which holds the first primary election of the 2008 presidential contest tomorrow."

"The groundswell of support kept his campaign afloat."

From ground + swell.