Arguendo is a Latin term meaning "in arguing" or "for the sake of argument". When one assumes something arguendo, the person is asserting a hypothetical statement to be true for the purpose of argument, regardless of whether that statement is actually true or whether they believe it to be true.
The term arguendo often appears in court opinions when a judge wants to express that, even if a party’s argument is correct, they still will not win the case.
[Last updated in June of 2022 by the Wex Definitions Team]