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 memo has caused a rift between President Donald Trump and his MAGA base, who have long promoted conspiracy theories tied to Epstein and his 2019 death behind bars. —Solcyré Burga, Time, 14 July 2025

When your worldview is based on a conspiracy theory, anything that doesn’t align with that theory becomes another conspiracy. —Bill Goodykoontz, AZCentral.com, 14 July 2025

Reports showed far-right supporters spreading conspiracy theories accusing Biden of complicity contributing to a spike in political threats and violence in late 2024. —Theo Burman, MSNBC Newsweek, 13 July 2025

The release was intended to address conspiracy theories about Epstein’s apparent suicide in federal custody. —Dhruv Mehrotra, Wired News, 11 July 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