Usurp, v. t. [imp. & p. p. Usurped; p. pr. & vb. n. Usurping.]
Etymology: [L. usurpare, usurpatum, to make use of, enjoy, get possession of, usurp; the first part of usurpare is akin to usus use (see Use, n.): cf. F. usurper.]
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. Alack, thou dost usurp authority. Shak. Another revolution, to get rid of this illegitimate and usurped government, would of course be perfectly justifiable. Burke.
Note: Usurp is applied to seizure and use of office, functions, powers, rights, etc.; it is not applied to common dispossession of private property.
Syn. -- To arrogate; assume; appropriate.
1 other Webster entry under this spelling
Usurp, 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. The parish churches on which the Presbyterians and fanatics had usurped. Evelyn. And now the Spirits of the Mind Are busy with poor Peter Bell; Upon the rights of visual sense Usurping, with a prevalence More terrible than magic spell. Wordsworth.
Shades of meaning
Fernald has no entry of its own for usurp; he lists it under assume.
Where he writes about it:
He may assume authority or office that is his right; if he assumes what does not belong to him, he is said to arrogate or usurp it. — from assume
A man may usurp the substance of power in the most unpretending way; what he arrogates to himself he assumes with a haughty and overbearing manner. — from assume