Source : Free On-Line Dictionary of Computing

Mask Read-Only Memory
     
         (MROM) A kind of {ROM} in which the memory contents
        are determined by one of the masks used to manufacture the
        {integrated circuit}.  MROM can give high storage density
        (bits per millimeter squared) making it a cheap solution for
        high volume applications.
     
        [Other ROM types?]
     
        (1995-04-22)