Peace of mind; relief; a feeling of being free from worry or anxiety (used as a noun, na-adjective, or suru-verb).
子どもの帰宅を確認して、やっと安心した。
I finally felt relieved after confirming my child had returned home.
この保険に入っていれば安心だと思う人が多い。
Many people feel secure thinking that having this insurance is enough.
安心して休んでください。
Please rest without worry.