a leap in the dark

US /ə liːp ɪn ðə dɑːrk/
UK /ə liːp ɪn ðə dɑːrk/
"a leap in the dark" picture
1.

暗闇への飛躍, 未知への挑戦

an act or decision whose consequences are unknown and potentially dangerous, but which is undertaken anyway

:
Starting a new business without a clear plan is often a leap in the dark.
明確な計画なしに新しいビジネスを始めることは、しばしば暗闇への飛躍です。
She decided to move to a new country without a job offer, which was a leap in the dark.
彼女は仕事のオファーなしに新しい国へ引っ越すことを決めたが、それは暗闇への飛躍だった。