earthnutEnglishOxford New American Dictionaryearthnut /ˈərTHˌnət, ˈərθˌnət / ▸ noun 1 a Eurasian plant of the parsley family, which has an edible roundish tuber and is found in woodland and acid pasture. Also called pignut. Conopodium majus, family Umbelliferae. ▪ the almond-flavored tuber of the earthnut plant. 2 British another term for peanut.