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

In the months leading up to her death, Babbitt excitedly expressed pro-Trump conspiracy theories on social media. —Brian Niemietz, New York Daily News, 3 May 2025

The Trump administration's CIA reported earlier in 2025 that a lab leak was the likely origin of the COVID-19 virus, which had been passed off by media outlets and scientists as a likely conspiracy theory during the early days of the pandemic. —Louis Casiano, FOXNews.com, 1 May 2025

Sanders’ multi-day ordeal was marked by conspiracy theories, tirades and constant debate. —Jacob Feldman, Sportico.com, 29 Apr. 2025

And that direct link is the fact that antisemitism is a conspiracy theory, in contrast to any other form of discrimination. —Isaac Chotiner, New Yorker, 22 Apr. 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