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

First up was Ben Shapiro, who described Tucker Carlson and others as grifters and charlatans, guilty of misleading their audiences with falsehoods and conspiracy theories. —Jonathan J. Cooper, Fortune, 19 Dec. 2025

After years of debate, investigations and conspiracy theories, the Department of Justice is scheduled on Friday to finally release the Jeffrey Epstein files. —Julie K. Brown, Miami Herald, 18 Dec. 2025

Bongino made his name over the past decade as a pro-Trump, far-right podcaster who pushed conspiracy theories, including some involving the FBI. —Ryan Lucas, NPR, 17 Dec. 2025

And conspiracy theory believers are a sizable portion of the conservative coalition. —Emily Brooks, The Hill, 16 Dec. 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