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

Wide SCSI

    A variant on the SCSI-2 interface.  It
   uses a 16-bit bus - double the width of the original SCSI-1
   - and therefore cannot be connected to a SCSI-1 bus.  It
   supports transfer rates up to 20 MB/s, like Fast SCSI.

   There is also a SCSI-2 definition of Wide-SCSI with a 32 bit
   data bus.  This allows up to 40 megabytes per second but is
   very rarely used because it requires a large number of wires
   (118 wires on two connectors).  Thus Wide SCSI usually means
   16 bit-wide SCSI.

   (1995-04-21)