When Pigs Fly—A Funny Proverb or an Unachievable Thing?

Photo of author

Alison Page

Alison has worked full-time in the writing industry for over ten years, using her knowledge and life experience to create online content, fiction and non-fiction. Alison has published two novels and has ghost-written several non-fiction equestrian books for a client. Alison has been a full-time professional content writer for almost ten years and loves her work as a wordsmith.

When pigs fly is an idiom used to describe something very unlikely to happen, something only a gullible person would believe, or something highly improbable.

Idioms like when pigs fly are phrases or expressions with meanings that cannot be directly inferred from the literal interpretation of their individual words; instead, they express a figurative meaning. They inject humor or interest into our conversation and writing. These English language idioms are often used in everyday, casual conversation rather than in a formal setting.

In this article, I’ll dive into the idiom’s deeper meaning, uncover its origin, and explain its correct usage. I’ll also provide tips for effective usage, along with a few sentence examples and related terms and phrases. After reading the guide, test your knowledge with our fun quiz. Let’s get started!

When Pigs Fly—A Funny Proverb or an Unachievable Thing

What Does the Idiom When Pigs Fly Mean?

The idiom when pigs fly is used to say that something is highly improbable or unlikely to happen or an event that only someone easily fooled would believe. It is often used to convey skepticism about the likelihood of a particular event or circumstance occurring in the foreseeable future.

Collins Dictionary says, “If you say when pigs fly after someone has said that something might happen, you are emphasizing that you think it is very unlikely.” Along similar lines, Merriam-Webster states that the idiom is used “to say that one thinks that something will never happen.”

My sister in Canada was chatting to me recently about the heavy snowfall they had last Christmas and how beautiful everything looked blanketed in the white stuff. I retorted that we would be expecting snow here in the balmy UK when pigs fly! Needless to say, no flying pigs were sighted in the skies over my house, and it rained all through the Christmas holiday!

Variations of the Idiom

The following phrases are variations of when pigs fly. You can use these expressions to spice up your conversation with a little easy humor and irony.

  • Pigs might fly
  • When pigs have wings
  • And pigs will fly
  • Pigs have to fly
  • Pigs may fly

How Is When Pigs Fly Commonly Used in Context?

When pigs fly is a humorous idiom you often hear in casual conversations among friends and family or in informal written work. This phrase is not generally used in academic or professional settings.

Here are some handy ways and tips on how to incorporate the idiom into your conversation and writing, together with a few examples of its use:

What Are the Different Ways to Use the Idiom When Pigs Fly?

  • Expressing unlikelihood: “My son will clean his room voluntarily? Yeah, sure, when pigs fly.”
  • Humorous response: “My husband will certainly admit when he’s wrong. Ha! When pigs fly!”
  • Skepticism: “A politician keeping all their promises? That’ll happen when pigs fly.”
  • Expressing impossibility: “Getting everyone in the family to agree on a movie? When pigs fly, my friend, when pigs fly.”
  • Unrealistic conditions: “You can borrow my favorite vintage LP when pigs fly.”
  • Expressing doubt: “The team thinks they’ll get promoted this season? Yeah, when pigs fly.”

What Are Some Tips for Using the Idiom When Pigs Fly Effectively?

  • Context is important: Be sure to use the phrase in circumstances where the contrast is clear between reality and what’s being said.
  • Tone of voice: Use a sarcastic or playful tone of voice to match the level of humor or disbelief you want to convey and enhance the effect of the expression.
  • Timing is critical: Use the expression at just the right moment to respond to particularly unlikely or surprising statements for maximum impact.
  • Use humor: Use the phrase in a light-hearted, playful manner and humorous context to convey a sense of amusement and make your audience laugh. 
  • Know your audience: Ensure your audience understands your intended meaning and be mindful of the social and cultural context of the conversation. Idioms can have different interpretations in different regions, countries, and settings.
  • Avoid overuse: If you use the idiom too frequently, it will lose its effectiveness and impact, so keep it for situations where it adds value or consider using an alternative.

Where Can You Find Examples of When Pigs Fly?

This is a casual phrase that’s generally used in fun situations and in daily conversation. You also see this idiom used in different media, such as in movies, TV shows, online, books, and even public speeches.

Here are some examples of when pigs fly used in popular media:

We probably all have used the phrase ‘when pigs fly’ at one time or another to refer to something we thought was impossible, right? (The Norwalk Reflector)

She said: “And there are those who say that pigs will fly before you get Theresa May’s deal through Parliament.” (The Daily Express)

What Is the Origin of the Idiom When Pigs Fly?

When Pigs Fly Ngram
When pigs fly usage trend.

The idiom when pigs fly has its roots in an expression found in John Withal’s A Shorte Dictionarie for Yonge Begynners, a Latin-English dictionary published in 1916:

“Pigs fly in the ayre with their tayles forward.”

The idea here is that pigs are flying through the air backward, which, of course, is highly improbable. This is considered a Scottish proverb, making it impossible to know the phrase’s true age and origin.

How Did the Idiom Evolve Over Time?

Over time, the idiom evolved to become associated with derision or ridicule, so you should only use it among friends who are gently teasing each other. This phrase is not suitable for use in more formal correspondence and could be taken as offensive if used in the wrong context.

When pigs fly is an adynaton, which is a figure of speech that is so hyperbolic that it is impossible.

What Are Some Related Terms to When Pigs Fly?

It can be helpful to understand how to use the idiom in context if you’re familiar with some related terms, including antonyms and synonyms. 

When Pigs Fly—A Funny Proverb or an Unachievable Thing 2


  • When hell freezes over
  • When fish climb trees
  • When a snowball survives in snow
  • When cats bark
  • When rivers flow uphill
  • When the check is in the mail
  • When a leopard changes its spots


When Pigs Fly: Test Your Knowledge!

Choose the correct answer.

What Have We Learned About When Pigs Fly?

When pigs fly is an idiom that means something is highly unlikely to happen, unfeasible, or totally improbable. 

The phrase was first published in a Latin-English dictionary in 1916, although it’s thought to come from an old Scottish proverb of uncertain date. When pigs fly is the American version of the idiom, while pigs might fly is more commonly used in British English. However, both expressions mean the same thing.

An idiom is a phrase or expression with a figurative meaning not easily deduced from its literal definition. When pigs fly is meant to be used in a humorous, slightly derisory way when conversing with someone you know well. 

The expression is not considered suitable for formal or academic situations and should always be used in the correct context.