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 maneuvers were spotted, using ADS-B Exchange data and ATC recording, by conspiracy theory debunking website Metabunk, reported on by The Warzone and posts from the flight tracking X account Thenewarea51 (@thenewarea51). —Barbara A. Perry, Newsweek, 28 Jan. 2025

Caroline Kennedy’s son, Jack Schlossberg, has been particularly outspoken on social media about RFK Jr., who has advanced conspiracy theories about the JFK and RFK assassinations. —Ted Johnson, Deadline, 28 Jan. 2025

On the social media platform X, the images sparked conspiracy theories about human trafficking at the site because of the message and because the location is near a shipping yard. —Ruben Vives, Los Angeles Times, 28 Jan. 2025

These historic challenges are amplified by the spread of misinformation, disinformation, and conspiracy theories that blur the line between facts and fiction. —Juan Manuel Santos, TIME, 28 Jan. 2025

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