Source : Webster's Revised Unabridged Dictionary (1913)

Chaplain \Chap"lain\, n. [F. chapelain, fr. LL. capellanus, fr.
   capella. See {Chapel}.]
   1. An ecclesiastic who has a chapel, or who performs
      religious service in a chapel.

   2. A clergyman who is officially attached to the army or
      navy, to some public institution, or to a family or court,
      for the purpose of performing divine service.

   3. Any person (clergyman or layman) chosen to conduct
      religious exercises for a society, etc.; as, a chaplain of
      a Masonic or a temperance lodge.

Source : WordNet®

chaplain
     n : a clergyman ministering to some institution