removable disk

from WordNet (r) 3.0 (2006)

removable disk
    n 1: a hard disk that can be removed from the disk drive;
         removal prevents unauthorized use

from The Free On-line Dictionary of Computing (8 July 2008)

removable hard disk
removable disk

   <storage> A type of {magnetic disk}, or possibly
   {magneto-optical disk} which is not permanently attached to
   the {disk drive} (not a {fixed disk}) but which can be taken
   out and replaced, allowing many disks to be used in the same
   drive.

   The term "removable disk" would seem to be applicable to
   {floppy disks} but is generally reserved for {hard disks} in
   suitable cartridges such as those made by {Syquest}, {Iomega}
   and others.

   Removable disk packs were common on {minicomputers} such as
   the {PDP-11} in use in the 1970s except that the drives were
   the size of {washing machines} and the disk packs as big as
   car wheels.  Removable disks became popular on
   {microcomputers} in the 1990s as a cheap way of expanding disk
   space, transporting large amounts of data between computers
   and storing {backups}.  Large, cheap fixed hard disks and {USB
   memory sticks} have made removable disks less attractive.

   (2007-06-14)