XYY syndrome

[ĕks′wī-wī]
n.
  1. A chromosomal anomaly characterized by the presence of one X-chromosome and two Y-chromosomes and thought to be associated with tallness, aggressiveness, and acne.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.