gold standard
noun
1- historical the system by which the value of a currency was defined in terms of gold, for which the currency could be exchanged. The gold standard was generally abandoned in the Depression of the 1930s.〈史〉金本位制（在此制度下, 通货基本单位与一定数量的黄金价值相同, 并可与之兑换; 20世纪30年代大萧条中被普遍放弃）。
1.1
- figurative the best or most prestigious thing of its type〈喻〉同类中最好（或最有声望的）东西：
breast milk provides the gold standard by which infant feeds are measured.
母乳是最好的婴儿食品。