Being in an early period of life, development, or growth. Newly begun or formed; not advanced: The evening is still young. Of, belonging to, or suggestive of youth or early life: He is young for his age. Vigorous or fresh; youthful. Lacking experience; immature: a young hand at plowing. Being the junior of two people having the same name. Geology Being of an early stage in a geologic cycle. Used of bodies of water and land formations. Young persons considered as a group; youth: entertainment for the young. Offspring; brood: a lioness with her young. with young Pregnant. Used of an animal.