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

Legal experts said the slow pace reflects a cautious approach by Graf, the large volume of evidence and a desire by prosecutors to disprove conspiracy theories around the case. — Matthew Brown, Chicago Tribune, 13 Aug. 2026

Bush and his cabinet emerge at the end, however, to reveal that this conspiracy theory is itself a conspiracy, one perpetuated by the government. — Damon Wise, Deadline, 13 Aug. 2026

To this day, conspiracy theories alleging that Jonestown was a CIA mind-control experiment gone awry find favor across the internet. — James Kirchick, The Atlantic, 13 Aug. 2026

During his time on Miller’s podcast, the secretary also discussed fatherhood and conspiracy theories. — Claire Carter, The Washington Examiner, 12 Aug. 2026

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