he·mo·glo·bin (h??m?-gl??b?n)n. The protein in the red blood cells of vertebrates that carries oxygen from the lungs to tissues and that consists of four polypeptide subunits, each of which is bound to an iron-containing heme molecule.[Ultimately short for hematinoglobulin : hematin + globulin.]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.he?mo?glo?bin (?hi m??glo? b?n, ?h?m ?-) n. a conjugated protein in red blood cells, comprising globin and iron-containing heme, that transports oxygen from the lungs to the tissues of the body. [1865?70; earlier hematoglobulin. See hemo-, globin] he`mo?glo?bic, adj. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.he·mo·glo·bin (h??m?-gl??b?n) An iron-containing protein in the blood of many animals that, in vertebrates, carries oxygen from the lungs to the tissues of the body and carries carbon dioxide from the tissues to the lungs. Hemoglobin is contained in the red blood cells of vertebrates and gives these cells their characteristic color. Hemoglobin is also found in many invertebrates, where it circulates freely in the blood. See Note at red blood cell.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.hemoglobin1. An oxygen-carrying pigment found in the red blood cells of vertebrate animals.2. The iron-rich, oxygen-transporting pigment in red blood cells which gives them their color.Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited