The Collaborative International Dictionary of English v.0.48:

Ostiary \Os"ti*a*ry\, n.; pl. -ries. [L. ostium door,
   entrance. See Usher.]
   1. The mouth of a river; an estuary. [R.] --Sir T. Browne.
      [1913 Webster]

   2. One who keeps the door, especially the door of a church; a
      porter. --N. Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ostiary
    n 1: the lowest of the minor Holy Orders in the unreformed
         Western Church but now suppressed by the Roman Catholic
         Church [syn: doorkeeper, ostiary, ostiarius]
    2: someone who guards an entrance [syn: doorkeeper, doorman,
       door guard, hall porter, porter, gatekeeper,
       ostiary]