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

The eerie connection to Havana Syndrome enhances the series' sense of realism, blurring the lines between conspiracy theory and credible threat. —Gordon G. Chang, Newsweek, 4 Mar. 2025

What began last year as an unfounded conspiracy theory targeting Haitian immigrants living legally in the U.S. has escalated, with the Trump Administration recently instituting a harsh reality against the legal Haitian immigrants. —Jared McCallister, New York Daily News, 1 Mar. 2025

Jack Posobiec, a right-wing influencer who rose to prominence by pushing conspiracy theories such as Pizzagate, was invited by Pentagon officials to travel on Hegseth’s first trip overseas. —Ali Breland, The Atlantic, 28 Feb. 2025

These riots were caused in part by a false conspiracy theory claiming the murderer of three girls at a dance class was a Muslim terrorist who came from outside the UK. —Max Goldbart, Deadline, 27 Feb. 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