Under the thumb Informal

Completely under someone else’s control or influence, whether a specific person, a group, or a broader authority.

Unlike the closely related ’under someone’s thumb,’ this more general form can describe domination by an institution, government, or circumstance, not only by an individual.

Like its close relative “under someone’s thumb,” the idiom refers to the physical action of pressing something down firmly and securely with a thumb, holding it under complete control. The two forms — with and without a specific possessive — have coexisted in English for centuries and are often used interchangeably, though “under the thumb” lends itself slightly more naturally to describing control by something other than a single named person.

The small country remained under the thumb of its powerful neighbor for decades.

Employees felt they were under the thumb of an overly strict manager.

He’s been under the thumb of that gang since he was a teenager.

A: Why doesn’t the company innovate? B: It’s under the thumb of overly cautious investors.