na-adjective, noun
sound health; robust health; vigorous
Literary or somewhat formal word describing a person's strong, healthy constitution. Often used in set phrases like 勇健な体.
祖父は90歳にしては勇健だ。
My grandfather is in robust health for a 90-year-old.
彼の勇健な体は若い頃の鍛錬の賜物だ。
His vigorous body is the fruit of training in his youth.