noun
great mistake; serious error; blunder; complete misunderstanding
Emphasizes a very large or fundamental mistake, often with a nuance of surprise or criticism. Can refer to factual errors, misjudgments, or complete misunderstandings.
それは大間違いだ。
That's a huge mistake.
彼の説明を聞いて、大間違い
After hearing his explanation, I realized my serious error.
そんなことを信じるなんて大間違いだ。
Believing something like that is a complete misunderstanding.