1. The act of pouring from one container into another one; hence, transference, or the transmission of something: Frank tipped the pitcher of lemonade in order to complete the transfusion of the drink from the container to his glass.
2. In medicine, the transfer of a body fluid from one person, or animal, to the veins of another person, or animal: A transfusion involves the injection of blood or a blood component into the bloodstream.

The transfusion of large volumes of life-saving liquid into the bloodstream is also done primarily to remedy someone who has bled severely after an accident or has lost a lot of blood during surgery.

During a transfusion, the patient's pulse, blood pressure, and temperature are measured regularly and, if there are any signs of bad reactions, the transfusion is discontinued.

A procedure for collecting and storing a patient's own blood several weeks before its expected need by the patient: This method of providing blood, or autologous transfusion, for an individual is done in order to prevent the transmission of diseases which can take place with the use of donor blood.

Blood that is lost during a surgical procedure can be recovered from the operation site and processed for the circulatory system when a patient's autologous transfusion is available.

A transfer of vital bodily fluid that is obtained from a dead body within a short time after a person's death: Cadaver blood transfusion is acceptable for movement into other living humans.

The movement of blood directly from one person to another one: Direct transfusion is the medical process of a person’s vital body fluid being given straight from the donor to the recipient by using an interconnecting hollow tube.

The transfer and withdrawal of small amounts of blood that is repeated until the blood volume is almost entirely exchanged: "Exchange transfusions are used for infants who are born with hemolytic disease (the abnormal breakdown of red blood cells) and in patients with uremia (a form of blood poisoning caused by the accumulation in the blood of products that are normally eliminated in the urine)."

A transfusion of blood from a donor to a suitable storage container and then to the patient.