A groundswell is a rising of public feeling that gathers force. A groundswell of support, a groundswell of anger, a real groundswell.
It nearly always takes of and always names something rising from below rather than organised from above. The literal sense is a broad deep swell in the sea, raised by a distant storm rather than the local wind.
1noungroundswellA rising of public feeling that gathers force.
“A groundswell of public anger forced the government to change its plans.”
groundswell is a movement.
Ground plus swell, from the deep sea swell raised by a distant storm.
From ground + swell.
Etymology from Wiktionary, CC BY-SA