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 site has a history of promoting groundless conspiracy theories. —Tom Dreisbach, NPR, 20 Feb. 2025

Fort Knox has long been the subject of conspiracy theories regarding its contents. —Tom Rogers, Newsweek, 20 Feb. 2025

Now, the conspiracy theory might be that those in uniform for Kansas City were not the real Chiefs since their play was so bad! —Los Angeles Times, 15 Feb. 2025

Zoom in: King's assassination at the Lorraine Motel in Memphis has long fueled conspiracy theories about potential government involvement, especially because of the FBI's hostility toward him. —Marc Caputo, Axios, 15 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