High-density diskette
A 3.5" floppy diskette capable of holding up to 1.44 megabytes of data or a 5.25" diskette capable of holding up to 1.2 megabytes of data.
A high-density diskette can be distinguished from others either by the labeling of a 1.44 or 1.2 megabytes label or the initials of HD on the diskette. Today, most computer stores only carry high-density diskettes.
Also see: Floppy definitions