The Collaborative International Dictionary of English v.0.48:

Myrmecophyte \Myr"me*co*phyte`\, n. [Gr. my`rmhx, my`rmhkos, ant
   + fyto`n plant.] (Bot.)
   A plant that affords shelter and food to certain species of
   ants which live in symbiotic relations with it. Special
   adaptations for this purpose exist; thus, Acacia
   spadicigera has large hollows thorns, and species of
   Cecropia have stem cavities. -- Myr`me*co*phyt"ic, a.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

myrmecophyte
    n 1: plant that affords shelter or food to ants that live in
         symbiotic relations with it