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

The pollster and the newspaper described the lawsuit as a conspiracy theory and an affront to free speech protections. — Hannah Fingerhut, Los Angeles Times, 23 Sep. 2026

But while chemtrails are firmly in the realm of conspiracy theory, electromagnetic fields and radio frequency radiation exposure have been studied for decades. — Stephanie Pappas, Scientific American, 22 Sep. 2026

The two got married in April, CBS reported, and Danis also became the subject of unfounded conspiracy theories alongside her new husband. — Rebekah Riess, CNN Money, 21 Sep. 2026

Fox's attorneys noted that Rupert Murdoch had been auto-deleting all of his text messages until about April 2022, which was after Dominion had filed its lawsuit against Fox for broadcasting unfounded conspiracy theories about the 2020 election. — Maddy Lauria, NPR, 20 Sep. 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