open letter
noun [ C ] uk/ˌəʊ.pən ˈlet.ər/ us/ˌoʊ.pən ˈlet̬.ɚ/
公开信
a letter intended to be read by a lot of people, not just the person it is written to
An open letter to the prime minister, signed by several MPs, appeared in today's papers. 在今天的报纸上登载了一封有好几位议员签名的致首相的公开信。