Any of a number of stone artefacts, usually around 30 cms (12 inches) high, carved in the form of a mushroom cap supported by the figure of an animal, god, etc., found in Guatemala and occasionally elsewhere in Mesoamerica.
Mushroom stones are chiefly Mayan in origin and have been dated between approximately 1500 b.c. and 900 a.d. They are believed to be associated with the ritual use of hallucinogenic mushrooms.
Mid 17th century (in an earlier sense). From mushroom + stone.