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

On her 18th studio album, In Time of Dragons, Amos draws on the long tradition of reptilian imagery to symbolize the elite, from ancient myth to David Icke’s conspiracy theories. —Emma Madden, Pitchfork, 30 Apr. 2026

Over the course of three decades, multiple law enforcement agencies tried to crack the case as conspiracy theories involving complex gang and music-related rivalries swirled. —Clara Harter, Los Angeles Times, 29 Apr. 2026

The site best known for dragging conspiracy theories into mainstream political discourse was put on the market after its architect filed for bankruptcy in 2022. —Brittany Allen, Literary Hub, 29 Apr. 2026

Distrust in legacy media and the rise of unregulated social media have helped make conspiracy theories a routine feature of the discussion about major public incidents. —Max Tani, semafor.com, 28 Apr. 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