“A thing or matter that has been finally decided on its merits (as between the parties) by a court having jurisdiction of the subject of the litigation and of the defendant if the judgment is a personal one against him and that cannot be litigated again between the same parties called also former adjudication.”
Source: Webster’s Third New International Dictionary
“A matter adjudged; a thing judicially acted upon or decided; a thing or matter settled by judgment. Rule that a final judgment rendered by a court of competent jurisdiction on the merits is conclusive as to the rights of the parties and their privies, and, as to them, constitutes an absolute bar to a subsequent action involving the same claim, demand or cause of action. And to be applicable, requires identity in thing sued for as well as identity of cause of action, of persons and parties to action, and of quality in persons for or against whom claim is made. The sum and substance of the whole rule is that a matter once judicially decided is finally decided. Allen v McCurry, 449 U.S. 90.”
Source: Black’s Law Dictionary, 6th Edition