conspiracy theory


plural conspiracy theories
: a theory that explains an event or set of circumstances as the result of a secret plot by usually powerful conspirators
the conspiracy theories surrounding Kennedy's assassination
also : a theory asserting that a secret of great importance is being kept from the public
… is best known for … his conspiracy theory that a secret cabal of reptilian humanoids is running the world. Simon Little
… has often been criticized for promoting conspiracy theories such as "birtherism," the theory that President Obama was not born in the U.S. Grace Segers

Example Sentences

Conspiracy theories sprung up soon after the leader's assassination.
Recent Examples on the Web District Attorney Brooke Jenkins debunked several other aspects of the conspiracy theory as well, saying there's no evidence DePape knew Paul Pelosi, and saying Pelosi was alone at home when DePape broke in. David Klepper, ajc, 1 Nov. 2022 The tenets of conspiracy theory have increasingly been mainstreamed by conservative politicians and media personalities, according to the UMass poll directors. Hayley Kaufman,, 27 Oct. 2022 In 2020, the revelation that Caryn and her husband Michael Borland are supporters of the conspiracy theory led to the cancellation of a Montana fundraiser. Iris Samuels, Anchorage Daily News, 18 Oct. 2022 Many commenters took the post as proof that monkeypox was a hoax or otherwise part of a conspiracy theory rather than a legitimate health concern. Molly Stellino, USA TODAY, 22 Sep. 2022 People who study QAnon don't find Trump's overt embrace of the baseless conspiracy theory to be a laughing matter. Peter Weber, The Week, 20 Sep. 2022 Polling shows that QAnon remains popular, with roughly 41 million Americans believing core tenets of the conspiracy theory, according to a 2021 poll from the Public Religion Research Institute. New York Times, 25 July 2022 Many commentators suggested that Musk might be afraid of former President Bill Clinton and his wife, former Secretary of State Hillary Clinton, playing off of the conspiracy theory that the Clintons were involved in Jeffrey Epstein's suicide. Fox News, 9 May 2022 Cox has spread the baseless claims that former President Donald Trump won the 2020 election, and has amplified the QAnon conspiracy theory. CBS News, 8 Nov. 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'conspiracy theory.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

First Known Use

1863, in the meaning defined above

Time Traveler
The first known use of conspiracy theory was in 1863

Dictionary Entries Near conspiracy theory

Cite this Entry

“Conspiracy theory.” Dictionary, Merriam-Webster, Accessed 4 Dec. 2022.

Kids Definition

conspiracy theory


: a theory that explains an event or situation as being the result of a secret plot
conspiracy theorist noun
Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Challenging Words You Should Know

  • hedgehog reading a book
  • Often used to describe “the march of time,” what does inexorable mean?
How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

Universal Daily Crossword

A daily challenge for crossword fanatics.