sincere and earnest; showing genuine, serious feeling or attitude.
彼はミスについて真摯に謝った。
He sincerely apologized for the mistake.
問題は真摯な姿勢で話し合うべきだ。
The issue should be discussed with an earnest/sincere attitude.
彼女はその仕事に真摯に取り組んでいる。
She is tackling that work earnestly.