Cool someone's heels

Cool someone's heels

Meaning:

Wait for a long time.

If you cool your heels, someone makes you wait for a long time with nothing to do, so you get bored or impatient.

Example:

While they were having a long meeting, Mary was cooling her heels waiting for the results.

The show was so popular that I had to cool my heels in a long line at the box office.