Source : Webster's Revised Unabridged Dictionary (1913)

Cola nut \Cola nut\, Cola seed \Cola seed\ . (Bot.)
   The bitter fruit of {Cola acuminata}, which is nearly as
   large as a chestnut, and furnishes a stimulant, which is used
   in medicine.

Source : WordNet®

cola nut
     n : bitter brown seed containing caffein; source of cola extract
         [syn: {kola nut}]