(n)reaction of the body to a transfusion of blood that is not compatible with its own blood; an adverse reaction can range from fever and hives to renal failure and shock and death
The Collaborative International Dictionary of English (GCIDE) v.0.53Collaborative International Dictionary (GCIDE)
n. [ L. transfusio: cf. F. transfusion. ] 1. The act of transfusing, or pouring, as liquor, out of one vessel into another. Howell. [ 1913 Webster ]
2. (Med.) The act or operation of transferring the blood of one man or animal into the vascular system of another; also, the introduction of any fluid into the blood vessels, or into a cavity of the body from which it can readily be adsorbed into the vessels; intrafusion; as, the peritoneal transfusion of milk. [ 1913 Webster ]