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

But if the evidence shows Aspiration merely wanted to pay Leonard to get his endorsement, a conspiracy theory involving Ballmer and the Clippers would take a hit. —Michael McCann, Sportico.com, 5 Sep. 2025

His promotion of conspiracy theories claiming vaccines cause autism, linking antidepressants to school shootings and even suggesting WiFi causes cancer alarmed healthcare professionals and Democratic lawmakers. —Swapna Venugopal Ramaswamy, USA Today, 4 Sep. 2025

As Deadline previously reported, Slavin drew backlash within crew communities recently for some controversial comments on social media that include disparaging language about undocumented immigrants and conspiracy theories about the coronavirus pandemic. —Katie Campione, Deadline, 4 Sep. 2025

Deus Ex also dabbles in conspiracy theories, which Metal Gear Solid fans will surely be familiar with and enjoy. —George Yang, Vulture, 3 Sep. 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