1. (Science: pharmacology) Capable of harmonious coexistence, of medications, suitable for simultaneous administration without nullification or aggravation of the effects of either.
2. (Science: haematology) Denoting a donor and recipient of a blood transfusion in which there is no transfusion reaction.
3. (Science: immunology) histocompatible, denoting a donor and recipient of an organ transplant that is not rejected.