1. right away; immediately; at once; without delay; willing at any moment

1. Lou would have gone to the football game at the drop of a hat.

2. She loses her temper at the drop of a hat.

3. Those workmen look for any reason to stop working. They’ll put down their tools at the drop of a hat.

4. Nancy really doesn’t want to stay in her present job. She’ll leave for another one at the drop of a hat.