A transitive verb meaning to calm or quiet someone/something; to help someone compose themselves (similar to 落ち着かせる or the transitive use of 落ち着く).
深呼吸をさせて、まず子どもを落ち着けた。
I had him take a deep breath and first calmed the child down.
重要な発表の前に、同僚を落ち着けるために一言かけた。
Before the important announcement, I said a few words to calm my colleague.
動揺している彼を落ち着けるのは簡単ではない。
It's not easy to calm him when he's upset.