What is Arguendo?

Legal Definition
Arguendo is a Latin legal term meaning for the sake of argument. "Assuming, arguendo, that ..." and similar phrases are used in courtroom settings and academic legal settings, and occasionally in other domains, to designate provisional and unendorsed assumptions that will be made at the beginning of an argument in order to explore their implications.
-- Wikipedia
Legal Definition
A Latin term meaning "in arguing" or "for the sake of argument". When one assumes something arguendo, the person is asserting a hypothetical or other statement for the purpose of argument.
Legal Definition
In arguing; in the course of the argument. A statement or observation made by a judge as a matter of argument or illustration, but not directly bearing upon the case at bar or only incidentally involved in it, is said (in the reports) to be made arguendo, or, in the abbreviated form, arg.
-- Black's Law Dictionary
Legal Definition
In argument; by way of argument.
-- Ballentine's Law Dictionary