earthnut

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

• noun A Eurasian and northern African plant (Conopodium majus) in the parsley family, having tuberous roots that are edible when roasted.
• noun The tuber of this plant.
• noun Any of various other plants, such as the peanut, similar to the earthnut.

from The Century Dictionary.

• noun The tuberous root of Bunium flexuosum and B. Bulbocastanum, common umbelliferous plants of Europe. See Bunium.
• noun The groundunt, Arachis hypogæa.
• noun The tuber of Cyperus rotundus and some other species of the same genus.

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

• noun The esculent tubers of the umbelliferous plants Bunium flexuosum and Carum Bulbocastanum.
• noun The peanut. See peanut.

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

• noun Any of various roots, tubers, or pods that grow underground.

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

• noun a common European plant having edible tubers with the flavor of roasted chestnuts
• noun edible subterranean fungus of the genus Tuber
• noun any of various highly prized edible subterranean fungi of the genus Tuber; grow naturally in southwestern Europe
• noun pod of the peanut vine containing usually 2 nuts or seeds; `groundnut' and `monkey nut' are British terms