Source : Webster's Revised Unabridged Dictionary (1913)

Oratory \Or"a*to*ry\, n.; pl. {Oratories}. [OE. oratorie, fr. L.
   oratorium, fr. oratorius of praying, of an orator: cf. F.
   oratoire. See {Orator}, {Oral}, and cf. {Oratorio}.]
   A place of orisons, or prayer; especially, a chapel or small
   room set apart for private devotions.

         An oratory [temple] . . . in worship of Dian.
                                                  --Chaucer.

         Do not omit thy prayers for want of a good oratory, or
         place to pray in.                        --Jer. Taylor.

   {Fathers of the Oratory} (R. C. Ch.), a society of priests
      founded by St. Philip Neri, living in community, and not
      bound by a special vow. The members are called also
      {oratorians}.