floppy disk

noun
1.
Computers. a thin plastic disk coated with magnetic material, on which computer data and programs can be stored for later retrieval.
Also, floppydisk.
Also called floppy, diskette, flexible disk, magnetic disk.
Origin
1970-75; called floppy from the fact that the earliest disks are ‘flexible’, though the later (3.5 inch) disks have a rigid plastic case
British Dictionary definitions for floppy disks

floppy disk

noun
1.
a flexible removable magnetic disk that stores information and can be used to store data for use in a microprocessor Also called diskette, flexible disk
floppy disks in Science
floppy disk
  (flŏp'pē)   
A flexible plastic disk coated with magnetic material and covered by a protective jacket, used for storing data. Floppy disks were once the principal storage medium for personal computers, but inexpensive hard disks and writable compact disks have greatly diminished their role.