What is child? What is child? A person between birth and puberty.A person who has not attained maturity or the age of legal majority.An unborn infant; a fetus. An infant; a baby.One who is childish or immature.A son or daughter; an offspring.A member of a tribe; descendant: children of Abraham. An individual regarded as strongly affected by another or by a specified time, place, or circumstance: a child of nature; a child of the Sixties. A product or result of something specified: "Times Square is a child of the 20th century” ( Richard F. Shepard). with child Pregnant.