Of a person: that has the mental or physical characteristics of someone younger; youthful; esp. retaining the enthusiasm or energy of the young…

Resembling, having the qualities of, or suitable for someone young; youthful.

(a) n. an old person who has the mental or physical characteristics of one who is younger (rare before 20th cent.); (b) adj. that appears both…

Having youth or the characteristics of youth: = youthful, adj. 1.

(a) adj. resembling or having the character of youth, juvenile (cf. youthly, adj.); (b) adv. like a youth, or in the manner of youth.

Having or characterized by youth; that is still young.

Having the bright or lively eyes of a young person. Frequently figurative (chiefly poetic): energetic, lively, enthusiastic; naive; new.

youthful in disposition, juvenile.

Having or affecting the character of youth: usually connoting a youthful appearance or behaviour inconsistent with the person's years.

Used by Byron for: youthful, young. Obsolete.