Definition of "XX"

XX¹

numeral
1. A Roman numeral representing the number 20.

XX²

adjective
1. (biology) Having a female configuration of chromosomes as per the XY system.
  Quotations
  An autosomal recessive gene causes gonadal dysgenesis in XX individuals, and several distinct entities have been identified.
  2001, Kenneth L. Becker (ed), Principles and Practice of Endocrinology and Metabolism (in English), page 857
  If a Y chromosome is present in an XX-karyotyped individual, gonadal removal is necessary due to the risk of gonadoblastoma.
  2007, Fima Lifshitz (ed), Pediatric Endocrinology, Volume 2 (in English), page 358
  The group at John Hopkins[sic], as well as many others, dropped the "true sex" policy (such as XX or XY) and adopted the "optimal gender" policy for assigning sex to sexually ambiguous children.
  2009, Gerald N. Callahan, Between XX and XY: Intersexuality and the Myth of Two Sexes (in English), page 30
2. (biology) Synonym of ZZ (“having a male configuration of chromosomes as per the ZW system”)

XX³

adjective
1. (clothing) Extra large, a garment size