code word
noun [ C ] uk/ˈkəʊd ˌwɜːd/ us/ˈkoʊd ˌwɝːd/
代号
a word or sign with a special meaning, or a word used to keep something secret
"Long" and "frank" are all diplomatic code words for continuing disagreement. “长时间的”和“坦率的”都是外交上表示持续分歧的代名词。