AT THE DROP OF A HAT

{adv. phr.}, {informal} 1. Without waiting; immediately; promptly. * /If you need a babysitter quickly, call Mary, because she can come at the drop of a hat./ Compare: ON THE SPUR OF THE MOMENT. 2. Whenever you have a chance; with very little cause or urging. * /At the drop of a hat, he would tell the story of the canal he wanted to build./ * /He was quarrelsome and ready to fight at the drop of a hat./