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

Executives appear worried the attacks are driven by conspiracy theories linking 5G cell towers to health risks, a concern that also sparked similar vandalism against cell sites during the COVID-19 pandemic. —PC Magazine, 9 Oct. 2025

Historic Fox News settlement Dominion Voting Systems -- the voting machine company at the center of false 2020 election fraud conspiracy theories -- has been sold to a seemingly new election company run by a former Republican election official, according to a person familiar with the sale. —Olivia Rubin, ABC News, 9 Oct. 2025

The very last thing the world needs is another conspiracy theory, but hoo-boy, Chiefs fans could concoct one about ESPN’s broadcasters. —Pete Grathoff, Kansas City Star, 9 Oct. 2025

TikTok brims with both clever and crazed conspiracy theories. —Kieran Press-Reynolds, Pitchfork, 8 Oct. 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