Dimly; faintly; indistinctly — not clearly seen or defined.
遠くの山々が朝霧でぼんやり見える。
The distant mountains look faintly visible in the morning mist.
暗くて看板の文字がぼんやりして読めない。
It's so dark the sign's letters are indistinct and I can't read them.
記憶がぼんやりして細かいところを覚えていない。
My memory is vague; I don't remember the details.
Absentmindedly; vacantly; in a daze — inattentive or lost in thought.
彼は授業中にぼんやりしてノートを取っていなかった。
He was daydreaming in class and didn't take notes.
買い物に行って財布を忘れてきたことに、家に着いてからぼんやりと気づいた。
I only absentmindedly realized I had left my wallet at home after getting back.
朝はいつもぼんやりしていて、顔を洗ってからでないと頭がはっきりしない。
I'm always a bit out of it in the morning; my head doesn't clear until I wash my face.
Idly; aimlessly — spending time without purpose or energy.
休日は何もせずにテレビを見てぼんやり過ごした。
I spent the day off idly watching TV with nothing else to do.
窓の外をぼんやり眺めて時間だけが過ぎていった。
I just stared out the window absentmindedly as time passed.
A person who is absentminded or dull-witted; a blockhead (colloquial).
また鍵を忘れたの？本当にぼんやりだね。
You forgot your keys again? You're really absentminded.
先生は彼を少しぼんやりな生徒だと言った。
The teacher said he was a somewhat absentminded student.