Conspiracy Theory:
1. The act of conspiring.
2. An evil, unlawful, treacherous, or surreptitious plan formulated in secret by two or more persons; plot.
3. A combination of persons for a secret, unlawful, or evil purpose: He joined the conspiracy to overthrow the government.
4. Law. an agreement by two or more persons to commit a crime, fraud, or other wrongful act.
5. Any concurrence in action; combination in bringing about a given result.