cola nut

from The Century Dictionary.

• noun A brownish bitter seed, of about the size of a chestnut, produced by a tree of western tropical Africa, Cola acuminata, natural order Sterculiaceœ.

from the GNU version of the Collaborative International Dictionary of English.

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

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun bitter brown seed containing caffein; source of cola extract