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

But in the months since, Owens has pushed conspiracy theories about his murder and made unfounded fraud allegations about the finances at Turning Point, which Erika Kirk now runs. —CBS News, 11 Dec. 2025

The two sat in chairs facing each other for a conversation that lasted more than 50 minutes and spanned topics from DOGE to Musk’s thoughts on AI, social media, conspiracy theories and fashion. —Bill Barrow, Fortune, 11 Dec. 2025

Under his leadership, the CDC has been forced to replace decades of advances in science with conspiracy theories on vaccines, autism, HIV/AIDS, fluoride, Tylenol and even Wi-Fi. —MSNBC Newsweek, 11 Dec. 2025

Set in the small, fictional town of Eddington, NM, the script immediately immerses the audience in the chaos of that summer, examining the breakdown of social culture fueled by fear, misinformation and conspiracy theories. —Robert Lang, Deadline, 11 Dec. 2025

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