Source : Webster's Revised Unabridged Dictionary (1913)

Stepping-stone \Step"ping-stone`\, n.
   1. A stone to raise the feet above the surface of water or
      mud in walking.

   2. Fig.: A means of progress or advancement.

            These obstacles his genius had turned into
            stepping-stones.                      --Macaulay.

            That men may rise on stepping-stones Of their dead
            selves to higher things.              --Tennyson.