earthstarEnglishOxford New American Dictionaryearthstar /ˈərTHstär, ˈərθstɑr / ▸ noun a brownish woodland fungus with a spherical spore-containing fruiting body surrounded by a fleshy star-shaped structure, found in both Eurasia and North America. Family Geastraceae, class Gasteromycetes: Geastrum and other genera.