Proper
Reasonable
noun, な adjective
Everything is calm and right. It is proper and reasonable.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
彼が嫌いだと言うわけじゃないんだけど、あそこであの発言はちょっと穏当でないなと思ったわけよ。
It’s not that I don’t like him, I just thought his remarks at the time were improper.