con·spir·a·cy 
(k
ən-spîr
ə-s
ē)
n. pl. con·spir·a·cies 1. An agreement to perform together an illegal, wrongful, or subversive act.
2. A group of conspirators.
3. Law An agreement between two or more persons to commit a crime or accomplish a legal purpose through illegal action.
4. A joining or acting together, as if by sinister design: a conspiracy of wind and tide that devastated coastal areas.
[Middle English conspiracie, from Anglo-Norman, probably alteration of Old French conspiration, from Latin cōnspīrātiō, cōnspīrātiōn-, from cōnspīrātus, past participle of cōnspīrāre, to conspire; see CONSPIRE.]