na-adjective, noun
Dated term for a relaxed, worry-free state. Still understood but less common in modern conversation; 気楽 or のんびり are more typical today.
隠居してからは安気な毎日を送っている。
Since retiring, I've been living a carefree life every day.
彼はいつも安気そうにしている。
He always seems so at ease.
Compound of 安 (peace, ease) and 気 (spirit, mood). The exact historical derivation is uncertain, but the meaning follows naturally from the kanji components.