gamma globulin also gam·ma·glob·u·lin 
(găm′ə-glŏbyə-lĭn)
(găm′ə-glŏbyə-lĭn)n.
1. Any of a group of globulins in blood plasma that in an electrophoretic separation of serum proteins migrate the most slowly toward the anode. Most antibodies (immunoglobulins) are gamma globulins.
2. The protein fraction of blood serum that contains the gamma globulins.
3. See immune globulin.