To make an agreement, esp. a secret agreement, to do some act, as to commit treason or a crime, or to do some unlawful deed; to plot together.
- To plan together secretly to commit an illegal or wrongful act or accomplish a legal purpose through illegal action.
- To join or act together; combine: "Semisweet chocolate, cocoa powder, espresso, Cognac, and vanilla all conspire to intensify [the cake's] flavor” ( Sally Schneider).
- To plan or plot secretly.