(law) An exception whereby the defendant can claim that the matter has already been adjudged and cannot be re-visited.
"The gist of the defence of res judicata is that the matter or question which is being raised by an adversary has previously been finally adjudicated upon in proceedings between the same parties, and cannot be raised again. A matter is res judicata when the prior judgment was given (1) with respect to the same subject-matter, (2) based on the same ground, and (3) between the same parties." CONSOL LTD t/a CONSOL GLASS v TWEE JONGE GEZELLEN (PTY) LTD AND ANOTHER (2) 2005 (6) SA 23 (C)