conspiracy theory

noun

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

Examples of conspiracy theory in a Sentence

Conspiracy theories sprung up soon after the leader's assassination.

Recent Examples on the Web

And some conspiracy theories about a lack of water for firefighting center around the billionaire owners of The Wonderful Company, Stewart and Lynda Resnick. —Julia Simon, NPR, 15 Jan. 2025

Such a strategy should not simply dismiss pet owners’ concerns as conspiracy theories, but should instead adopt a thoughtful approach that takes individuals’ specific concerns seriously. —Simon F. Haeder, The Conversation, 14 Jan. 2025

That’s the same system that Mark Zuckerberg revealed last week for Meta, which is preparing to fire its third-party professional fact-checkers who are already straining against a flood of conspiracy theories. —Allison Morrow, CNN, 14 Jan. 2025

Fact check: Post distorts Defense Department contract with COVID-19 conspiracy theory The claim that MrBeast was awarded taxpayer money as part of a recruiting push is wrong on multiple fronts, according to both the Department of Defense and to Donaldson. —Joedy McCreary, USA TODAY, 9 Jan. 2025

Word History

First Known Use

1863, in the meaning defined above

Kids Definition

conspiracy theory

noun

: a theory that explains an event or situation as being the result of a secret plot

conspiracy theorist noun