throm·bo·cy·to·pe·ni·a (thr?m?b?-s??t?-p??n?-?)n. An abnormally low level of platelets in the circulating blood.throm?bo·cy?to·pe?nic adj.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.thrombocytopenia (??r?mb???sa?t???pi?n??) n (Pathology) pathol an abnormal decrease in the number of platelets in the blood[C20: from German thrombocytopenie from thrombocyte + Greek penia poverty]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014throm?bo?cy?to?pe?ni?a (??r?m bo??sa? t??pi ni ?) n. an abnormal decrease in the number of blood platelets. [1920?25] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.