The Collaborative International Dictionary of English v.0.48:

Antiphonary \An*tiph"o*na*ry\, n. [LL. antiphonarium. See
   Antiphoner.]
   A book containing a collection of antiphons; the book in
   which the antiphons of the breviary, with their musical
   notes, are contained.
   [1913 Webster]

WordNet (r) 3.0 (2006):

antiphonary
    adj 1: relating to or resembling an antiphon or antiphony [syn:
           antiphonary, antiphonal]
    n 1: bound collection of antiphons [syn: antiphonary,
         antiphonal]