1Completely; totally; used to emphasize that something is wholly the case (often used with negatives to mean 'not ... at all').
問題の意味が全く分からない。
I don't understand the meaning of the problem at all.
彼の説明は全く適切だった。
His explanation was completely appropriate.
この計画は全く失敗に終わった。
This plan ended in complete failure.
2Used to express agreement or strong emphasis, meaning 'indeed' or 'exactly'.
まったく、その通りだ。
Indeed, that's exactly right.
全くその考えには賛成できない。
I can't agree with that idea at all.
3An interjection expressing exasperation or annoyance (like 'good grief' or 'honestly').
まったくもう、約束を守ってよ！
Good grief—keep your promise!
まったく、信じられない話だ。
Honestly, it's an unbelievable story.