na-adjective, noun
healthy; robust; in good health
Describes a person's physical condition as strong and healthy, often used in formal or written contexts. Can also be used as a noun.
祖父は90歳だが、まだ壮健だ。
My grandfather is 90, but he is still healthy and robust.
壮健な体を維持するには運動が欠かせない。
Exercise is essential to maintain a healthy body.
Compound of 壮 (sō, 'vigorous, robust') and 健 (ken, 'healthy'). The exact historical derivation is uncertain, but the combination naturally conveys robust health.