Wikipedia
Superformatting
Superformatting is the process of formatting a floppy disk at a capacity that the disk is not designed for. It can ruin a floppy disk, but it is used in some floppy-based Linux distros to increase the room for applications and utilities. muLinux is a notable example of this technique. Another common use (which is not as popular nowadays) was to format low-density 3½ inch or 5¼ inch floppies as high-density, or in the case of 3.5 disks, even extended density (HD-36.) "Notched" disks will usually turn up a lot of bad sectors, especially if the formatted capacity is considerably (1.5 to 3) times higher than intended. Superformatting is usually done with a low-level format (such as "format /u" in DOS and "fdformat" in Linux.)