platelet factor 3

n.
  1. A phospholipid lipoprotein blood coagulation factor derived from platelets that acts with certain plasma thromboplastin factors to convert prothrombin to thrombin.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.