The Collaborative International Dictionary of English v.0.48:

mamoncillo \mamoncillo\ n.
   A tropical American tree (Melicocca bijuga, or Melicocca
   bijugatus) bearing a small edible fruit with green leathery
   skin and sweet juicy translucent pulp.

   Syn: Spanish lime, Spanish lime tree, honey berry, genip,
        ginep, Melicocca bijuga, Melicocca bijugatus.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

mamoncillo
    n 1: tropical American tree bearing a small edible fruit with
         green leathery skin and sweet juicy translucent pulp [syn:
         Spanish lime, Spanish lime tree, honey berry,
         mamoncillo, genip, ginep, Melicocca bijuga,
         Melicocca bijugatus]