earth-ball

(noun) any of various highly prized edible subterranean fungi of the genus Tuber; grow naturally in southwestern Europe. Synonyms: truffle, earthnut.

(noun) any of various fungi of the genus Scleroderma having hard-skinned subterranean fruiting bodies resembling truffles. Synonyms: earthball, false truffle, puffball, hard-skinned puffball.