u·sur·pa·tion 
(y′sər-pāshən, -zər-)
(y′sər-pāshən, -zər-)n.
1. The act of usurping, especially the wrongful seizure of royal sovereignty.
2. A wrongful seizure or exercise of authority or privilege belonging to another; an encroachment: "in our own day, gross usurpations upon the liberty of private life" (John Stuart Mill).