another think coming

The phrase "another think coming" is an idiomatic expression used to indicate that someone's belief or assumption is incorrect, and they need to reconsider or rethink their position. It often implies that the person is being unrealistic or mistaken in their understanding. The phrase originated as a shortened version of the saying "If that's what you think, you've got another think coming," which is a form of warning or correction to someone's false belief.