Source : Webster's Revised Unabridged Dictionary (1913)

Gatepost \Gate"post`\, n.
   1. A post to which a gate is hung; -- called also {swinging
      or hinging post}.

   2. A post against which a gate closes; -- called also
      {shutting post}.

Source : WordNet®

gatepost
     n : either of two posts that bound a gate