APA Dictionary of Psychology

a relatively rare disorder in which a male inherits the full complement of both male and female sex chromosomes instead of either the normal two X chromosomes (46, XX) for females or the normal one X and one Y chromosome (46,XY) for males. Affected individuals have a normal penis but small testes and prostate, and about half develop enlarged breasts and have intellectual and developmental disabilities. Also called 48,XXXY syndrome.