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

Once Harrison traded Doncic to the L.A. Lakers for Anthony Davis, it re-set the way he is viewed, while crushing the spirit of every Mavericks fans and fueling every Ruby Ridge conspiracy theory that has ever existed about the NBA. —Mac Engel, Fort Worth Star-Telegram, 13 May 2025

The lottery has often been the subject of conspiracy theories, dating to the first iteration in 1985, when the New York Knicks moved up from the No. 3 spot to land Georgetown star Patrick Ewing. —Bob Harkins, New York Times, 13 May 2025

Last week, the Trump administration agreed to use the feed of One American News, or OAN — a far-right, ardently pro-Trump media network known for propagating conspiracy theories — on VOA and other services. —Christine Fernando, Los Angeles Times, 12 May 2025

This includes numerous conspiracy theories not supported by facts, because who cares about facts anyway. —Bruce Y. Lee, Forbes.com, 12 May 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