Source : Webster's Revised Unabridged Dictionary (1913)

Guidepost \Guide"post`\, n.
   A post at the fork of a road, with a guideboard on it, to
   direct travelers.

Source : WordNet®

guidepost
     n 1: a rule or principle that provides guidance to appropriate
          behavior [syn: {guideline}, {rule of thumb}]
     2: a post bearing a sign that gives directions or shows the way
        [syn: {signpost}]