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

Lockhart explores themes of mental illness, conspiracy theories and trauma with intelligence and compassion, and his writing is first-rate. —Michael Schaub, Los Angeles Times, 12 May 2026

Unfounded accusations and extremist conspiracy theories will not distract me from the work that matters. —Ashley Paul, CBS News, 12 May 2026

About 1 in 4 say the correspondents’ dinner shooting was staged, the poll found, including roughly a third of Democrats, as conspiracy theories spread widely online. —Liam Scott, Washington Post, 11 May 2026

On Saturday Night Live‘s Weekend Update, former Fox News host Tucker Carlson got triggered by the Met Gala in New York on Monday and developed a conspiracy theory about one of the 50 states. —William Vaillancourt, Rolling Stone, 10 May 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