素すっ頓とん狂きょう

na-adjective

wild; crazy; hysterical; freakish

Describes behavior, speech, or a situation that is absurdly wild, hysterical, or out of the ordinary. Often used for sudden, loud, or nonsensical outbursts. Can be used as a な-adjective or adverbially with に.

• 彼かれは素すっ頓とん狂きょうな声こえを上あげて笑わらい出だした。

  He burst out laughing with a wild, strange voice.

• 会かい議ぎ中ちゅうに素すっ頓とん狂きょうな質しつ問もんをして、みんなを驚おどろかせた。

  During the meeting, he asked a crazy question and surprised everyone.