Bethesda unit

[bə-thĕzdə]
n.
  1. A measure of inhibitor activity expressed as the amount of inhibitor that will inactivate 50 percent or 0.5 unit of a coagulation factor during a given incubation period.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.