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

In the absence of any definitive conclusion, conspiracy theories have blamed the homeless. —Robert Petkoff Krish Seenivasan Quinton Kamara, New York Times, 8 Apr. 2025

In 2021, Griswold launched an investigation into then-Mesa County Clerk Tina Peters following claims that the clerk, under the thrall of conspiracy theories of widespread voter fraud, granted unauthorized access to voting machines. —Nick Coltrain, Denver Post, 7 Apr. 2025

The podcast is considered to have shifted to the right in recent years, and has drawn criticism for its discussion of conspiracy theories and defense of controversial comments. —John W. Dean, MSNBC Newsweek, 7 Apr. 2025

But news of the child's death first came to light on Saturday, April 5—in a newsletter published by Robert Malone, an anti-vaccine advocate and peddler of conspiracy theories who came to prominence during the pandemic. —ArsTechnica, 7 Apr. 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