blood typen. See blood group.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.blood type n (Medicine) another name for blood group Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014blood? group` n. any of various classes into which human blood can be divided according to immunological compatibility based on the presence or absence of specific antigens on red blood cells. Also called blood type. Compare ABO system, Rh factor. [1915?20] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.blood type Any of the four main types into which human blood is divided: A, B, AB, and O. Blood types are based on the presence or absence of certain substances, called antigens, on red blood cells. Also called blood group.Did You Know? Blood transfusions used to be a doctor’s treatment of last resort, since they often caused people to get sick and die. But in the 1890s, a scientist named Karl Landsteiner began to solve the transfusion puzzle. He found that all human red blood cells belonged to one of four groups, or blood types, which he named A, B, AB, and O. The types refer to substances, called antigens, found on the surface of these cells. Antibodies circulating in a person’s blood normally recognize the antigens in that same person’s blood cells and don’t react with them. However, if a person with one blood type is given blood of another type, the antibodies bind to the foreign antigens, causing clumping of the blood and other serious reactions. Thus the key to the transfusion puzzle is to give a person blood that has matching antigens. Today, hospitals always test a blood sample before a transfusion to make sure there is a good match.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.blood typeAny of various types of blood (notably A, B, AB, O, Rh-positive, Rh-negative) named for the antigen(s) they do or do not contain. Mismatched blood transfusions cause adverse reactions in recipients.Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited