1. Capable of being mixed without undergoing destructive chemical change or exhibiting mutual antagonism; said of the elements in a properly constructed pharmaceutical mixture.
2. Denoting the ability of two biologic entities to exist together without nullification of, or deleterious effects on, the function of either; blood, tissues, or organs that cause no reaction when transfused or no rejection when transplanted.
3. Denoting satisfactory relationships between two or more people as in work or in marriage or in sexual activities.
The definition information for compatible is provided by Stedman's. You can search our medical dictionary here.