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

Absolutely Fabulous star Kathy Burke will discuss wellness, before the final episode sees Guz Khan dispensing nuggets of advice on conspiracy theories, wealth and other life matters. —Jesse Whittock, Deadline, 4 June 2026

Owens has become a particularly controversial figure after touting conspiracy theories pertaining to the death of conservative American activist Charlie Kirk and the gender of French first lady Brigitte Macron, who has filed a defamation lawsuit against the podcaster. —Zahra Ullah, CNN Money, 4 June 2026

There have been numerous conspiracy theories that Epstein was killed because of his connection to wealthy and powerful people. —Daniel Ruetenik, CBS News, 4 June 2026

That synagogue’s rabbis raised concern with a gubernatorial candidate’s ballot statement, which contained antisemitic conspiracy theories, earlier this election cycle. —Mathew Miranda, Sacbee.com, 3 June 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