Source : Webster's Revised Unabridged Dictionary (1913)

Eggplant \Egg"plant`\, n. (Bot.)
   A plant ({Solanum Melongena}), of East Indian origin, allied
   to the tomato, and bearing a large, smooth, edible fruit,
   shaped somewhat like an egg; mad-apple.

Source : WordNet®

eggplant
     n 1: egg-shaped vegetable having a shiny skin typically dark
          purple but occasionally white or yellow [syn: {aubergine},
           {mad apple}]
     2: hairy upright herb native to southeastern Asia but widely
        cultivated for its large glossy edible fruit commonly used
        as a vegetable [syn: {aubergine}, {brinjal}, {eggplant
        bush}, {garden egg}, {mad apple}, {Solanum melongena}]