Absent-mindedly; in a detached or blank way — a mimetic word for mumbling or speaking without much attention.
彼はぼそっと「まあいいか」と言って部屋を出た。
He muttered 'Oh well' absent-mindedly and left the room.
先生の説明を聞きながら、彼女はぼそっと別のことを考えていた。
While listening to the teacher's explanation, she was thinking about something else absent-mindedly.
疲れているときは、よくぼそっと独り言を言ってしまう。
When I'm tired I often end up muttering to myself absent-mindedly.
In a low voice; in undertones — speaking softly or murmuring, often barely audible.
彼女は怒っているのか、ぼそっと何か言っただけだった。
Whether she was angry or not, she only said something in a low voice.
会議中に誰かがぼそっと冗談を言って、みんなが笑った。
Someone murmured a joke during the meeting and everyone laughed.
彼は恥ずかしそうにぼそっと名前を呼んだ。
He shyly whispered her name under his breath.