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 when extreme weather happens, discourse on those conspiracy theories tend to spike, Wagner told CNN. —Ramishah Maruf, Brandon Miller, CNN, 25 Mar. 2025

Video As the deliberations dragged on, conspiracy theories abounded and speculation flourished. —Choe Sang-Hun, New York Times, 22 Mar. 2025

Speculation about such details surrounding Kennedy’s assassination has been intense over the decades, generating countless conspiracy theories about multiple shooters and involvement by the Soviet Union, the mafia and the CIA. —Jamie Stengle, Chicago Tribune, 19 Mar. 2025

He’s also spread right-wing conspiracy theories and aligned himself with Germany’s far-right AfD party. —Brian Niemietz, New York Daily News, 18 Mar. 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