1 A person under the age of majority. See also age. 2 Under the common law, a person who is under 14 child abuse years of age. 3 The son or daughter of a person or an individual who is treated as such. after-born child. A child born after a certain event, such as a child born after the execution of a will or the death of its testator parent. biological child. 1 A child born to his parents. Also called natural child. 2 A child genetically related to a specified parent. Also called genetic chil...