Collins COBUILD Advanced Learner's English Dictionary - engine room

(engine rooms) 1. On a boat or a ship, the engine room is the place where the engines are. N-COUNT 2. If you refer to something as the engine room of an organization or institution, you mean it is the most important or influential part of that organization or institution. These firms are regarded as the engine room of the British economy. N-COUNT: oft the N of n