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

In Tip Toe, Manchester gay bar owner Leo Struthers (Alan Cumming) and electrician neighbor Clive Goss’ (David Morrissey) feud takes a deadly turn when online conspiracy theories and anti-LGBTQ rhetoric come into play. — Glenn Garner, Deadline, 4 July 2026

Outraged critics say swapping AIPAC for Jews mimics the world's oldest antisemitic conspiracy theories, putting a terrifying target on Jewish backs. — Staff, FOXNews.com, 2 July 2026

Trump has boosted a conspiracy theory that Biden’s administration used the autopen without his knowledge to cover up his alleged senility. — Joseph Konig, PEOPLE, 2 July 2026

Ad tech companies dropped media outlets associated with Steve Bannon, Glenn Beck, and Tim Pool, all of whom had promoted conspiracy theories about the 2020 presidential election. — Literary Hub, 30 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