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 notion that the FBI orchestrated the Jan. 6 riot is a conspiracy theory that lacks evidence, The Associated Press has reported. —Joe Marusak, Charlotte Observer, 5 May 2024

The top prosecutor, a Republican who left the party to run in the nonpartisan DA election, has a history of supporting conspiracy theories about Antifa. —Will Carless, USA TODAY, 4 May 2024

Word History

First Known Use

1863, in the meaning defined above

Kids Definition

conspiracy theory

noun

: a theory that explains an event or situation as being the result of a secret plot

conspiracy theorist noun