How to use "when pigs fly"

What Does "when pigs fly" Mean?

The idiom "when pigs fly" is a sarcastic way of saying that something will never happen. Because pigs are heavy, land-bound animals without wings, the image of a flying pig represents a physical impossibility. When someone uses this phrase, they are expressing strong skepticism or a flat-out denial of a possibility.

• Idiomatic meaning: Never; an event that is impossible or highly unlikely to occur.
• Origin: The phrase has been used in various forms since the 17th century. An early version appeared in John Clarke's Paroemiologia Anglo-Latina (1639) as "pigs fly with their tails forward," used as a witty retort to an unbelievable statement.
• Register: Informal. It is frequently used in casual conversation, journalism, and creative writing to add a humorous or mocking tone.

How to Use It

"When pigs fly" usually functions as an adverbial phrase of time, often acting as a standalone retort or a dependent clause.

• Grammatical flexibility: It is most commonly used in the future tense ("It will happen when pigs fly") or as a punchline. While it can be modified slightly (e.g., "when pigs have wings"), the standard form is the most recognizable.
• What sounds unnatural: Avoid using it in formal academic or professional settings, as it can come across as dismissive or rude. Using it literally in a biological context is also incorrect, as it is strictly a figurative device. Additionally, negating the phrase (e.g., "pigs won't fly") usually destroys the idiomatic effect.

Real-World Examples

These examples are sourced from when pigs fly on Ludwig.guru.

""When pigs fly," University of Kansas political science professor Burdett Loomis said of Kobach." — huffingtonpost.com

"One Democratic legislator vowed that Sandy Springs would incorporate "when pigs fly," a phrase that Mayor Galambos has since adopted as the name of her blog." — nytimes.com

""I'll ask you to prom when pigs fly" And he said Yes! I met Ben Davis two years ago and ever since then we became really good friends." — huffingtonpost.com

"This could also mean Zune sync software for the Mac, something that we expected when pigs flew." — techcrunch.com

""Bukra Fi Mishmish" (When Pigs Fly) is a song by Palestinian And Israeli youth promoting peace and co-existence." — huffingtonpost.com

Similar Phrases and Alternatives

Phrase	Context
hell freezes over	Very informal and emphatic; suggests an impossibility based on a contradiction of terms.
not in a million years	Informal; emphasizes the extreme length of time that will pass without the event occurring.
don't hold your breath	Casual; used to tell someone that waiting for an event is a waste of time.
fat chance	Sarcastic and highly informal; means there is actually no chance at all.
highly improbable	Formal/Neutral; a literal and professional way to express skepticism.

Common Mistakes

• Literal misinterpretation: Some learners may think the phrase refers to an actual event involving animals. It is always used figuratively to denote impossibility.
• Register error: Learners often use it in the wrong register, failing to realize it is a highly informal and sometimes mocking way to say 'never'. Avoid using it with your boss or in a legal document.
• Tense confusion: While the phrase is usually "when pigs fly," using it in the past tense ("when pigs flew") is rare and usually only occurs when describing a past expectation of failure.

Quick-Reference Summary

Expression	Idiomatic Meaning	Register	Avoid In
When pigs fly	It will never happen	Informal / Sarcastic	Formal reports, professional emails, or serious academic writing

FAQs

Is when pigs fly ever used literally, or always figuratively?

This expression is almost exclusively used figuratively to describe an event that is impossible. While it might appear in works of fantasy or fiction involving magical creatures, in standard English conversation, it is a metaphorical tool for expressing total disbelief.

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How does this phrase differ from saying hell freezes over?

Both idioms mean "never," but hell freezes over is generally considered more emphatic and slightly more aggressive. While when pigs fly has a whimsical or humorous quality, the former is often used to express a stubborn refusal or a more intense level of skepticism.

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Can I use this expression in a business meeting?

No, you should exercise caution because learners often use it in the wrong register, failing to realize it is a highly informal and sometimes mocking way to say 'never'. Using it in a professional setting can make you sound unprofessional or derisive toward your colleagues' ideas.