Source : Webster's Revised Unabridged Dictionary (1913)

Greengage \Green"gage`\, n. (Bot.)
   A kind of plum of medium size, roundish shape, greenish
   flesh, and delicious flavor. It is called in France {Reine
   Claude}, after the queen of Francis I. See {Gage}.

Source : WordNet®

greengage
     n : sweet green or greenish-yellow variety of plum [syn: {greengage
         plum}]