a secret plan by a group of people to do something harmful or illegalconspiracy (to do something)a conspiracy to overthrow the governmentconspiracy (against somebody/something)conspiracies against the presidentconspiracy (to something)They were charged with conspiracy to murder.a conspiracy of silence(= an agreement not to talk publicly about something which should be made public)a conspiracy theory(= the belief that a conspiracy is responsible for a particular event)