|  | 
Medical Definition of Bird unit
1. A unit of prolactin activity: the minimal quantity of the hormone which will cause a certain increase in weight of the crop gland of pigeons. (05 Mar 2000)
|  | 
1. A unit of prolactin activity: the minimal quantity of the hormone which will cause a certain increase in weight of the crop gland of pigeons. (05 Mar 2000)