Main Entry: touch·stone

Pronunciation: \ˈtəch-ˌstōn\

Function: noun

Date: 1530

1 : a black siliceous stone related to flint and formerly used to test the purity of gold and silver by the streak left on the stone when rubbed by the metal
2 : a test or criterion for determining the quality or genuineness of a thing
3 : a fundamental or quintessential part or feature : basis <a touchstone film of that decade> <now considered a touchstone of the city's life — Michael Specter>

synonyms see standard