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

Those two storylines – Aiyuk’s bizarre estrangement since last September, and a conspiracy theory about players’ injuries linked to an electromagnetic field – should fizzle out as a new season arrives. — Cam Inman, Mercury News, 24 July 2026

Increasingly, his mind was preoccupied with extremist views and conspiracy theories, including secret government cabals and false-flag operations. — Connor Sheets, Los Angeles Times, 24 July 2026

One automatically ascribes fraud to results that are often predictable, even routine; the other dismisses legitimate concerns as conspiracy theories. — Andrew E. Busch, The Conversation, 23 July 2026

Conservative groups and social influencers have amplified that view through a whirlwind of covid conspiracy theories, bioterrorism fearmongering, and anti-immigration sentiment. — CNN Money, 22 July 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