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

Kovalchuk’s remarks show the depth of anti-Western feeling and sympathy for conspiracy theories within the Russian ruling elite. —James Bickerton, MSNBC Newsweek, 3 Oct. 2025

The lenient deal has since been the subject of widespread scrutiny and conspiracy theories—along with many other aspects of Epstein’s life and case. —Chantelle Lee, Time, 2 Oct. 2025

Court documents reviewed by Fox News Digital revealed that Edge espoused anti-LGBTQ conspiracy theories. —Sarah Rumpf-Whitten, FOXNews.com, 1 Oct. 2025

In January 2024, after coming under fire for reposting an antisemitic conspiracy theory on X, Musk visited Nazi concentration camps in Europe. —Hadas Gold, CNN Money, 29 Sep. 2025

Word History

First Known Use

1863, in the meaning defined above

Rhymes for conspiracy theory

• beery
• bleary
• cheery
• cirri
• dearie
• deary
• dreary
• eerie
• kiri
• leary
• leery
• peery

Kids Definition

conspiracy theory

noun

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

conspiracy theorist noun