The phrase "massive hunt" refers to a widespread and extensive search or pursuit for something or someone. It suggests that a large number of people or resources are being utilized to find or capture the target. Full definition
As Susannah says, it would require massive hunting for new titles — sorry Ralph Ellison, H.G. Wells got there first — and would require a major shift in the law. (slaw.ca)
The operation was a complete success and the men are now safe, despite a massive hunt by Free State forces.» (businessinsider.com)
When I make this dish each year I go on a massive hunt for shelled, pre-cooked chestnuts. (elanaspantry.com)