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

Brand now mixes prayer and conspiracy theory on Rumble livestreams, hawking adaptogenic mushroom supercoffee and more. — Luke Jones, Vanity Fair, 5 Nov. 2026

In 2022, Perry sought to invalidate Pennsylvania's electoral votes and elevate an acting attorney general who would act on conspiracy theories. — Michael Guise, CBS News, 3 Nov. 2026

Pat McCrory, a former Republican governor of North Carolina, is part of Right Count, a group of conservatives pushing back against election conspiracy theories and intervention in local elections. — Nicholas Riccardi, Los Angeles Times, 29 Oct. 2026

Pollution and purification have long been the focus of fringe Reddit forums and conspiracy theory dinner chat, but as of late, a broader consumer is feeling like there’s something in the water. — Tracy Achonwa, Vogue, 23 Oct. 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