The Collaborative International Dictionary of English v.0.48:

Lucuma \Lu*cu"ma\, n. (Bot.)
   An American genus of sapotaceous trees bearing sweet and
   edible fruits.
   [1913 Webster]

   Note: Lucuma mammosum is called natural marmalade in the
         West Indies; Lucuma Caimito, of Peru, furnishes a
         delicious fruit called lucuma and caimito.
         [1913 Webster]