The Collaborative International Dictionary of English v.0.48:

Scriptorium \Scrip*to"ri*um\, n.; pl. Scriptoria. [LL. See
   Scriptory.]
   In an abbey or monastery, the room set apart for writing or
   copying manuscripts; in general, a room devoted to writing.
   [1913 Webster]

         Writing rooms, or scriptoria, where the chief works of
         Latin literature . . . were copied and illuminated.
                                                  --J. R. Green.
   [1913 Webster]

WordNet (r) 3.0 (2006):

scriptorium
    n 1: a room in a monastery that is set aside for writing or
         copying manuscripts