aging-out, n. A foster child’s or minor ward’s reaching the age at which any legal right to care expires. • Aging-out usu. occurs when the child reaches the age of majority and becomes ineligible for foster care. Some states allow an extension of eligibility up to age 21 if the child is still in school or cannot live independently, or if it is otherwise in the child’s best interests to remain in foster care and the child consents. See INDEPENDENT-LIVING PROGRAM M.