u·ro·ki·nase (yo?or??-k??n?s, -n?z)n. An enzyme originally found in human urine that catalyzes the conversion of plasminogen to plasmin and is used in medicine to dissolve blood clots.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.urokinase (?j??r???ka?ne?z) n (Biochemistry) a biochemical catalyst present in urine and the blood streamCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014u?ro?ki?nase (?y??r ??ka? ne?s, -ne?z) n. an enzyme, present in the blood and urine of mammals, that activates plasminogen and is used medicinally to dissolve blood clots. [1955?60] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.