The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. A similar arrangement for registering the number of
      persons passing through a gateway, doorway, or the like.
      [1913 Webster]

WordNet (r) 3.0 (2006):

turnstile
    n 1: a gate consisting of a post that acts as a pivot for
         rotating arms; set in a passageway for controlling the
         persons entering

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "turnstile":
   French door, archway, back door, barway, bulkhead,
   carriage entrance, cellar door, cellarway, door, doorjamb,
   doorpost, doorway, front door, gate, gatepost, gateway, hatch,
   hatchway, lintel, porch, portal, porte cochere, postern,
   propylaeum, pylon, scuttle, side door, stile, storm door,
   threshold, tollgate, trap, trap door, turnpike