1. The act of claiming or taking something without the right to do so (some commentators argue that limited military actions unilaterally ordered by the President are an arrogation of Congress’s power to declare war).
2. Roman & civil law. The adoption of an adult; specif., the adoption of a person sui juris, as a result of which the adoptee loses independence and comes within the paternal power (patria potestas) of the adopting father. [Cases: Adoption
5. C.J.S. Adoption of Persons §§ 18–24.] — arrogate, vb.