そんなばかげた

such a ridiculous

→ そんな
phrase Rare #42,293
such a ridiculous Used before a noun to describe something as ridiculous, absurd, or foolish. ばかげた is the attributive form of ばかげている.
JA: そんなばかげた話を信じる人はいない。
EN: No one would believe such a ridiculous story.

彼女はそんなばかげた質問をするほど愚かではなかった

She wasn't foolish enough to ask such a ridiculous question.

私はそんなばかげた計画には反対したい

I want to oppose such a ridiculous plan.