https://www.dictionary.com/browse/conspiracy

the act of conspiring.

an evil, unlawful, treacherous, or surreptitious plan formulated in secret by two or more persons; plot.

a combination of persons for a secret, unlawful, or evil purpose: He joined the conspiracy to overthrow the government.

Law. an agreement by two or more persons to commit a crime, fraud, or other wrongful act.

any concurrence in action; combination in bringing about a given result.