na-adjective, noun
reckless; haphazard; blind; random
Describes acting without thinking, without a plan, or without clear direction. Often used adverbially as 闇雲に.
闇雲に突き進むのは危険だ。
It's dangerous to rush ahead recklessly.
彼は闇雲に本を買い集めている。
He is buying books haphazardly.