(1):
(v. t.) To seize, and hold in possession, by force, or without right; as, to usurp a throne; to usurp the prerogatives of the crown; to usurp power; to usurp the right of a patron is to oust or dispossess him.
(2):
(v. i.) To commit forcible seizure of place, power, functions, or the like, without right; to commit unjust encroachments; to be, or act as, a usurper.