What is an idiom?
An idiom is a natural manner of speaking to a native speaker of a language.

A Bird In The Hand Is Worth Two In The Bush:
Having something that is certain is much better than taking a risk for more, because chances are you might lose everything.

A Blessing in Disguise:
Something good that isn't recognized at first.

Baker's Dozen:
Thirteen.

Beat A Dead Horse:
To force an issue that has already ended.

Blue Moon:
A rare event or occurrence.

Can't Cut The Mustard:
Someone who isn't adequate enough to compete or participate.

Cast Iron Stomach:
Someone who has no problems, complications or ill effects with eating anything or drinking anything.

Charley Horse:
Stiffness in the leg / A leg cramp.

Chew someone out:
Verbally scold someone.

Chow Down:
To eat.