Admiration; being impressed by someone's actions, skill, or qualities (often used as '〜に感心する').
彼の問題解決の早さには感心した。
I was impressed by how quickly he solves problems.
子供たちの礼儀正しさに感心する。
I admire the children's politeness.
彼女は忙しいのにきちんと返信してくれて、本当に感心だ。
Even though she's busy she replies properly — it's truly admirable.
Admirable; praiseworthy — used adjectivally to say something deserves praise.
彼の誠実な態度は感心に値する。
His sincere attitude is worthy of admiration.
そんな献身的な行為は本当に感心だ。
Such a devoted act is truly admirable.
Astonishment or being appalled; often in negative form ('感心しない') expressing disapproval or that one is not impressed.
彼の無責任な態度には感心しない。
I'm not impressed by his irresponsible attitude. / I'm appalled by it.
そんなやり方では感心しないよ。
I'm not pleased with that method / That way of doing things doesn't impress me.