1. (noun)Klinefelter's syndrome, Klinefelter syndrome, XXY-syndrome syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced spermproduction and mental retardation; a genetic defect in which an extra X chromosome (XXY) is present in the male
Definition of 'klinefelter syndrome'
U.S. National Library of Medicine
1. klinefelter syndrome A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and maleinfertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tallstature. GYNECOMASTIA is present in many of the patients. The classicform has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns ( 46,XY/47,XXY; 47,XXY/48,XXXY, etc.).
Definitions of klinefelter syndrome 
