The phrase "massive rebellion" refers to a large-scale uprising or revolt where a lot of people actively defy or fight against a group, government, or authority. Full definition
But there were also several very high - profile retreats, over both last year's Queen's Speech and the Immigration Bill, in both cases seeing the Conservative part of the Coalition forced to allow backbenchers a free vote to avoid massive rebellions. (theconversation.com)
When we left fundamentalism nine years ago, I was overdue for a massive rebellion. (rachelheldevans.com)
Plans to replace the existing Lords with an 80 % elected second chamber had sparked a massive rebellion among Conservative MPs worried about the primacy of the Commons. (politics.co.uk)