mile·post
noun/ˈmaɪlpəʊst/
/ˈmaɪlpəʊst/
(especially North American English)- a post by the side of the road that shows how far it is to the next town, and to other places
里程标 - (also milestone British and North American English)a very important stage or event in the development of something
重要事件；重要阶段；转折点；里程碑