WordNet (r) 3.0 (2006):

Klinefelter syndrome
    n 1: syndrome in males that is characterized by small testes and
         long legs and enlarged breasts and reduced sperm production
         and mental retardation; a genetic defect in which an extra
         X chromosome (XXY) is present in the male [syn:
         Klinefelter's syndrome, Klinefelter syndrome, XXY-
         syndrome]