동문서답
東問西答 · asked about the east, answered about the west
An answer that has nothing to do with the question.
When to useSomeone dodging a question, or misunderstanding it completely.
Examples
숙제했냐고 물었더니 저녁 메뉴를 말하네, 완전 동문서답이야.
I asked if he did his homework and he told me what's for dinner — totally off topic.