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

Not just let him but goad him into spouting insane conspiracy theories about the previous election. —Annabella Rosciglione, Washington Examiner - Political News and Conservative Analysis About Congress, the President, and the Federal Government, 3 Sep. 2024

Joe Raedle | Getty Images Former President Donald Trump is facing a wave of calls from Republican supporters to focus his political attacks against Vice President Kamala Harris on policy critiques and to scale back his ad hominem insults and conspiracy theories. —Rebecca Picciotto, CNBC, 13 Aug. 2024

And a prolific booster of election conspiracy theories has used his work as the basis for a campaign to disrupt elections. —Phoebe Petrovic, Journal Sentinel, 9 Aug. 2024

That includes a long line of conspiracy theories and his claim that a worm ate part of his brain. —Brian Niemietz, New York Daily News, 8 Aug. 2024

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