usurp /yu̇-'sərp, -'zərp/ vb [Latin usurpare to take possession of without a strict legal claim, from usus use + rapere to seize]
vt: to seize and hold (as office, place, or powers) in possession by force or without right
the courts may not usurp the powers of the legislature
vi: to seize or exercise authority or possession wrongfully
usur·pa·tion /ˌyü-sər-'pā-shən, -zər-/ n
usurp·er /yu̇-'sər-pər, -'zər-/ n
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.