Unable to be settled or determined, often because it's too complicated or there isn't enough information.
The court found the case to be undecidable without further evidence.
裁判所は、さらなる証拠なしにはこの事件が決定できないと発見しました。
In math and logic, a problem or statement that you can't prove true or false no matter what, even with all the rules.
Some problems in math are undecidable, no matter how hard you try.
数学のいくつかの問題は、どれだけ努力しても決定できないものがあります。