释义
n.
a raised stone used singly or in a series as a place on which to step when crossing a stream or muddy area
（小溪、泥泞地的）踏脚石。
〈喻〉 垫脚石
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the school championships are a stepping stone to international competition .学校的锦标赛是进入国际比赛的垫脚石。
