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when pigs fly

/wen pɪɡz flaɪ/
idiom★Intermediate
informal

An expression used to indicate that something is extremely unlikely to happen or will never occur.

He said he'd clean his room when pigs fly.

This means he will never clean his room.

I'll finish this project by tomorrow, when pigs fly!

This sarcastically implies the project will not be finished on time.

💡

The phrase is often used humorously or sarcastically to express disbelief or skepticism about a claim.

Synonyms

Antonyms

Related Phrases

when hell freezes overidiom
An expression indicating that something will never happen.
not a snowball's chance in hellidiom
An expression indicating that something has no chance of happening.

💡Pro Tip

Context Matters

Use 'when pigs fly' in informal settings to express skepticism or disbelief. Avoid using it in formal or professional contexts.

⚡Gold Rule

Tone and Intent

The phrase is often used sarcastically, so ensure the tone matches the intended meaning to avoid misunderstandings.

📖Word Origin

The phrase originates from the idea that pigs, being unable to fly, make the scenario impossible, thus emphasizing the improbability of the event described.

📝Usage Notes

This idiom is commonly used in informal contexts to dismiss unrealistic or highly improbable statements. It can be used both seriously and humorously.

Word Breakdown

when
At the time that
subordinator
+
pigs
Domesticated animals known for their inability to fly
noun
+
fly
To move through the air using wings
verb
✎ Noted on May 31, 2026EN → EN

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