keep a lid on (something)

1. To keep the level of something from increasing drastically or beyond what is undesirable or dangerous. They were one of the few countries in the EU able to keep a lid on unemployment during the recession. The dictatorship has kept a tight lid on protests and public criticism of the government.

2. To not allow something to become known to other people; to keep something a secret or classified. No one else knows about it yet, so keep a lid on it for now. The company has so far kept a lid on details about its newest product.

keep a (or the) lid on

1 keep an emotion or process from going out of control. 2 keep something secret. informal

keep/put a/the ˈlid on something

try to make sure that people do not do something or find out about something: The government wants to keep the lid on discussion of tax reforms at the moment.