“Chase rainbows”

“Eat humble pie”

To admit that you were wrong.

“Cool as a cucumber”

Very calm, especially under pressure.

“Dirt cheap”

Very cheap.

“Come clean”

To tell the truth about something.

“Fair and square”

Honestly and according to the rules.

“Cry wolf”

To ask for help when there is no real danger, so people stop believing you.

“Crash course”

A short and intensive course.

“Dog days”

The hottest days of summer.