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 the conspiracy theories, rumors, and criticism tied to Lively at the Another Simple Favor premiere pale in comparison to the theories this group of obsessives have been circulating widely online since Lively’s legal battle against Baldoni began. —Stephanie McNeal, Glamour, 14 Mar. 2025

The perennial conspiracy theory that vaccines cause autism continues to spread. —Emma Woollacott, Forbes, 13 Mar. 2025

The jury that returned the potential record verdict against Jones concluded that the relatives of the Sandy Hook shooting victims were harassed and threatened for nearly a decade by audience members who subscribed to Jones’ conspiracy theories. —Edmund H. Mahony, Hartford Courant, 13 Mar. 2025

At the same time, Crookes suggests, American interest in the occult was morphing into a fascination with conspiracy theories. —Livia Gershon, JSTOR Daily, 10 Mar. 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