GNU Collaborative International Dictionary of English

Found one definition

1.       
   Mad-apple, Mad apple (?), n.
   1. (Bot.) The eggplant bush (Solanum melongena).  See Eggplant.
   
   Syn. -- eggplant, aubergine, brinjal, eggplant bush, garden egg, Solanum melongena.
   
   [1913 Webster + WordNet 1.5]
   
   
   2. The fruit of the eggplant bush, a large egg-shaped vegetable having a shiny skin typically dark purple but occasionally white or yellow.
   
   Syn. -- eggplant, aubergine.
   
   [WordNet 1.5]