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

Federal audits would, instead of protecting elections, allow a conspiracy theory to be weaponized into a way to keep legal voters from casting their ballot. —Los Angeles Times, 11 June 2026

Asked whether Jane’s Revenge had been designated a hate group, Fair again pointed to the SPLC’s standards, which include groups that vilify protected classes or promote anti-government conspiracy theories. —Kaelan Deese, The Washington Examiner, 9 June 2026

District leadership says a high school senior is facing disciplinary action after his quote inside the yearbook referenced a figure commonly associated with Holocaust conspiracy theories. —Mamie Bah, CBS News, 9 June 2026

Officials spent days tallying votes from the June 2 primary, typical in a state where slow counting has made the process a target for frustration and conspiracy theories. —ABC News, 9 June 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