groundnut

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A climbing vine (Apios americana) in the pea family, native to eastern North America, having compound leaves, clusters of fragrant brownish flowers, and small edible tubers.
• noun Any of several plants having underground tubers or nutlike parts.
• noun The tuber or nutlike part of such a plant.
• noun Chiefly British and South Atlantic US A peanut.

from The Century Dictionary.

• noun The ground-pea or peanut, the pod of Arachis hypogœa. See Arachis.
• noun The earthnut, the tuberous root of Bunium flexuosum, an umbelliferous plant of Europe.—3. The Apios tuberosa of the United States, a leguminous climber with small tuberous roots.

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

• noun United States, United States The fruit of the Arachis hypogæa (native country uncertain); the peanut; the earthnut.
• noun United States, United States A leguminous, twining plant (Apios tuberosa), producing clusters of dark purple flowers and having a root tuberous and pleasant to the taste.
• noun United States The dwarf ginseng (Aralia trifolia).
• noun A European plant of the genus Bunium (B. flexuosum), having an edible root of a globular shape and sweet, aromatic taste; -- called also earthnut, earth chestnut, hawknut, and pignut.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A climbing vine, Apios americana, of eastern North America, having fragrant brownish flowers and small edible tubers.
• noun Any similar plant having underground tubers.
• noun The nutlike tuber of such a plant; a peanut or monkey nut.

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

• noun pod of the peanut vine containing usually 2 nuts or seeds; `groundnut' and `monkey nut' are British terms
• noun a North American vine with fragrant blossoms and edible tubers; important food crop of Native Americans
• noun nutlike tuber; important food of Native Americans