ABO system ABO system /ˌeɪbiːˈoʊ ˈsɪstəm/

noun

1. A classification system for the antigens of human blood; used in blood transfusion therapy; four groups are A and B and AB and O  ( ABO blood group system , ABO group , ABO system )
   a classification system for the antigens of human blood; used in blood transfusion therapy; four groups are A and B and AB and O