Definitions for abo system
Random House Webster's College Dictionary
a classification of human blood into four major groups, A, B, AB, and O, based on the presence on the surface of red blood cells of either of two antigens, A or B, or their absence, O: used in determining compatibility for transfusions.
Origin of ABO system:
ABO blood group system, ABO system, ABO group(noun)
a classification system for the antigens of human blood; used in blood transfusion therapy; four groups are A and B and AB and O