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

Pollution and purification have long been the focus of fringe Reddit forums and conspiracy theory dinner chat, but as of late, a broader consumer is feeling like there’s something in the water. — Tracy Achonwa, Vogue, 23 Oct. 2026

Given that the dynamic between Europe and Russia is now characterized by pervasive mutual suspicion, conspiracy theories, and expectations of war, there is a growing danger of inadvertent escalation. — Dmitry Adamsky, Foreign Affairs, 21 Oct. 2026

In this tense political climate, Becker said, even straightforward election mistakes are magnified on social media and become the subject of conspiracy theories, making the job of local elections officials much more difficult. — Los Angeles Times, 20 Oct. 2026

In 2020, following Election Day, a crowd stormed a vote-counting center in Detroit, many incited by online conspiracy theories about election fraud. — ABC News, 20 Oct. 2026

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