Source : Webster's Revised Unabridged Dictionary (1913)

Earthnut \Earth"nut`\, n. (Bot.)
   A name given to various roots, tubers, or pods grown under or
   on the ground; as to:
   (a) The esculent tubers of the umbelliferous plants {Bunium
       flexuosum} and {Carum Bulbocastanum}.
   (b) The peanut. See {Peanut}.

Source : WordNet®

earthnut
     n 1: any of various highly prized edible subterranean fungi of
          the genus Tuber; grow naturally in southwestern Europe
          [syn: {truffle}, {earth-ball}]
     2: a common European plant having edible tubers with the flavor
        of roasted chestnuts [syn: {Conopodium denudatum}]
     3: pod of the peanut vine containing usually 2 nuts or seeds;
        `groundnut' and `monkey nut' are British terms [syn: {peanut},
         {goober}, {goober pea}, {groundnut}, {monkey nut}]
     4: edible subterranean fungus of the genus Tuber [syn: {truffle}]