HOL

As any witch or wizard who has experienced the Muggle world will tell you, when it comes to language, Muggles use some strange idioms.

However, Muggles are not the only ones; sometimes wizarding communities use their own magical idioms that are an alternative to the ones used by Muggles. For example :

Muggle idiom: "A Penny for your thoughts"
Magical alternative: A Knut for your thoughts

Muggle idiom: "The ball is in your court"
Magical alternative: The Bludger is in your court.

Muggle idiom:"Looking for a needle in a haystack"
Magical idiom: Looking for a wizard in an invisibility cloak.

Have you heard any of these magical idioms while you have been strolling through Diagon Alley or walking around the castle? Perhaps you have heard of other ones? If so please let us know

I heard of some the other day and though to mention it. Was something like:

Muggle idiom: "Bite the bullet"
Magical alternative: Chew the charm

Muggle idiom: "Fish out of water"
Magical alternative: Grindylow out of water

I have heard two magical idioms.
One is "Don't be such a Moaning Myrtle."
I heard someone at Hogwarts say it to another person. I think it means something close to "Don't be such a cry-baby."
The other is "It's either Horcruxes or Hallows."
I heard it at Diagon Alley.
I think it means something like "It's either this or that", where the speaker is indicating that there are only two possible alternatives.

Here are a couple I know:

Muggle Idiom: "All hands on deck."
Wizard Idiom: "All wands at the ready."

Muggle Idiom: "Dodged a bullet"
Wizard Idiom: "Dodged a bludger."

Muggle Idiom: "Elephant in the room."
Wizard Idiom: "Erumpent in the room."