/ Thesaurus / X Synonyms of xxy syndrome Find synonyms for: Noun1. Klinefelter's syndrome, Klinefelter syndrome, XXY-syndrome, syndromeusage: 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 maleWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: lyceum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language