1. in that This idiom is used after a statement to introduce an explanation. We choose this idiom to be more formal. He was lucky in that he had a lot of friends in that job. This book is very useful in that it explains everything very clearly. 2. up in the air If a plan or issue is up in the air , no decision has been made about it yet. Our wedding plans are still up in the air. That means we have not yet decided what we’ll do. The future of the business is still up in the air. The phrase up in the air is used to talk about something that is uncertain, often because other matters have to be decided first: 3. in hot water You are in hot water when you are in trouble because you have done something wrong. That will result in punishment or reprisal. You can be in hot water with the police if you break a law. A person can get into hot water for being late. The doctor was in hot water because he was exposed as a fake. That temper of hers can land her in hot water. The restaurant is...