Breadcrumb Home > Thesaurus > P Synonyms of prothrombin Find synonyms for: Noun1. prothrombin, factor II, coagulation factor, clotting factorusage: a protein in blood plasma that is the inactive precursor of thrombinWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of prothrombin (Dictionary) ✖ Related Content Daily Word Quiz: perambulate Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language