minidisk
/ˈmɪnɪdɪsk/noun
1(A virtual disk consisting of) a logical partition of a larger disk, especially on a mainframe computer.
2A floppy disk of a relatively small size; specifically a 5¼-inch (17cm) disk.
3Usually in form Minidisc. A trademark for: a magneto-optical disc resembling a small compact disc, which may be used to record sound or other data, or to play pre-recorded music, etc.
Origin
1970s; earliest use found in IBM Systems Journal. From mini- + disc.