hang on to your hat

[hang on to your hat] or [hold on to your hat] or [hold your hat]{v. phr.}, {informal} 1. Watch out; be prepared. - Used as a command,usually to warn of an unexpected action.

"Hold on to your hat,"said Jim as he stepped on the gas and the car shot forward.

2. Getready for a surprise. - Used as a command, usually to warn ofunexpected news.

"Hold on to your hat," said Mary. "Jim asked me tomarry him."