conspiracy theory

/kənˈspirəsi ˈθɪri/

/kənˈspirəsi ˈθɪəri/

Other forms: conspiracy theories

An unproven (and unlikely) belief that's based on a complex, secretive plot by powerful forces is a conspiracy theory. The idea that NASA faked the 1969 moon landing is one example of a conspiracy theory.

A theory is a set of unproven ideas, and a conspiracy is an illegal, covert plot. People who believe conspiracy theories are convinced that a corrupt government, or another equally powerful group, is secretly plotting to hide the truth, despite evidence to the contrary. There are wide-spread conspiracy theories about vaccines, global warming, Princess Diana's death, and the September 11, 2001 terrorist attacks, among many others.

Definitions of conspiracy theory

1. noun

   a belief that a secret group of people plotted together to cause an event or situation