expression, godan verb (-ku)
feel relieved; have one's worries dispelled
Literally 'to open one's worried eyebrows'; an idiomatic expression for relief after anxiety or trouble. Often used when a source of worry is resolved.
試験に合格して、やっと愁眉を開いた。
After passing the exam, I finally felt relieved.
彼の無事
Hearing that he was safe, his parents were relieved.