taru-adjective
Archaic taru-adjective describing a person's serene, unperturbed demeanor. Found mainly in classical literature; in modern Japanese, 悠然 or 落ち着いた are more common.
He remained composed and unruffled by anything.
In classical texts, it is sometimes used in phrases like 'a calm and composed attitude'.
The exact derivation is uncertain; the kanji 寛 (generous, lenient) and 然 (like, in the manner of) combine to form a classical taru-adjective meaning 'composed, calm'.