The Collaborative International Dictionary of English v.0.48:
Doorstep \Door"step`\, n. The stone or plank forming a step before an outer door. [1913 Webster]WordNet (r) 3.0 (2006):
doorstep n 1: the sill of a door; a horizontal piece of wood or stone that forms the bottom of a doorway and offers support when passing through a doorway [syn: doorsill, doorstep, threshold]