A settled and unalterable case; a final and irreversible verdict or decision.
经过专家组反复论证，这项研究结论已成南山铁案，毋庸置疑。
After repeated deliberations by the expert panel, this research conclusion has become a settled case, leaving no room for doubt.
Next Idiom
A settled and unalterable case; a final and irreversible verdict or decision.