mile.stone
n.(名词)A stone marker set up on a roadside to indicate the distance in miles from a given point.里程碑,里程标:路边所设立的石制标志,以英里指示从给定的一点到该路标的距离An important event, as in a person`s career, the history of a nation, or the advancement of knowledge in a field; a turning point.里程碑,转折点:在个人事业、国家的历史或某一领域知识的发展上所发生的重大事件;转折点