A plot to carry out some harmful or illegal act (especially a political plot) WordNet 3.0 & Open English WordNet

A conspiracy, also known as a plot, is a secret plan or agreement between people for an unlawful or harmful purpose, such as murder, treason, or corruption, especially with political motivation, while keeping their agreement secret from the public or from other people affected by it. Wikipedia

Secret act to obtain some goal, usually understood with negative connotations. Wikipedia Disambiguation

Secret plan or agreement for an unlawful or harmful purpose, especially with political motivation Wikidata

A clever scheme or artful plot, usually crafted for evil purposes. OmegaWiki

A secret plot. Wiktionary