1. Biochemistry. a lipoprotein in the blood that converts prothrombin to thrombin.
  2. Pharmacology. a commercial form of this substance, obtained from the brains of cattle, used chiefly as a local hemostatic and as a laboratory reagent in blood prothrombin tests.

Origin of thromboplastin

First recorded in 1910–15; thrombo- + -plast + -in2
Also called throm·bo·ki·nase [throm-boh-kahy-neys, -kin-eys] /ˌθrɒm boʊˈkaɪ neɪs, -ˈkɪn eɪs/. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for thromboplastin


  1. any of a group of substances that are liberated from damaged blood platelets and other tissues and convert prothrombin to thrombinAlso called: thrombokinase
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

thromboplastin in Medicine


  1. A plasma protein present in tissues, platelets, and white blood cells necessary for the coagulation of blood and, in the presence of calcium ions, necessary for the conversion of prothrombin to thrombin.factor III platelet tissue factor thrombokinase
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.