Source : Webster's Revised Unabridged Dictionary (1913)

Turnstile \Turn"stile`\, n.
   1. A revolving frame in a footpath, preventing the passage of
      horses or cattle, but admitting that of persons; a
      turnpike. See {Turnpike}, n., 1.

   2. A similar arrangement for registering the number of
      persons passing through a gateway, doorway, or the like.

Source : WordNet®

turnstile
     n : a gate consisting of a post that acts as a pivot for
         rotating arms; set in a passageway for controlling the
         persons entering