V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

XA
       eXtended Architecture (IBM, VM, ESA, VM/ESA, XC)


The Free On-line Dictionary of Computing (30 December 2018):

XA

   Extended Architecture

   A specification for drives which can play CD-ROMs in Green
   book CD-ROM format.

   (1994-12-06)