Absurd, irrelevant, or incoherent words or actions; something nonsensical or off the mark.
彼の説明はとんちんかんで、誰も理解できなかった。
His explanation was incoherent and no one could understand it.
そんなとんちんかんな返事は困るよ。もう少し本題に沿って話してくれ。
That irrelevant answer is a problem. Please stick to the main topic a little more.
頓珍漢な例を出したせいで、会議が混乱してしまった。
Because someone gave an absurd example, the meeting became confused.