a large block of stone that is put at the base of an important new public building in a special ceremony 基石，奠基石（重要公共建筑奠基典礼时放置） to lay the foundation stone of the new museum 为新建博物馆奠基
a basic or essential element of something 基石，奠基石（重要公共建筑奠基典礼时放置） Family life is one of the foundation stones of society. 家庭生活是社会的基石之一。