seize and take control without authority and possibly with force; take as one's right or possession; "He assumed to himself the right to fill all positions in the town"; "he usurped my rights"; "She seized control of the throne after her husband died"
If you say that someone usurps a job, role, title, or position, they take it from someone when they have no right to do this. Did she usurp his place in his mother's heart?. to take someone else's power, position, job etc when you do not have the right to (usurper, from usurpare , from usus ( USE) + rapere )
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
[ yu-'s&rp also -'z&a ] (verb.) 14th century. Middle English, from Middle French usurper, from Latin usurpare to take possession of without legal claim, from usually + rapere to seize; more at RAPID.