sacred cow
noun [ C ] disapproving uk/ˌseɪ.krɪd ˈkaʊ/ us/ˌseɪ.krɪd ˈkaʊ/
不容质疑的信仰;批评不得的习俗
a belief, custom, etc. that people support and do not question or criticize
They did not dare to challenge the sacred cow of parliamentary democracy. 他们不敢反对不容质疑的议会民主。