(also diskette), n. ~ A circular sheet of polyester (the disk) coated with magnetic oxide and housed in a thin, square plastic jacket that is used as a removable data storage medium.
The disk rotates within the jacket. An opening in the jacket provides the read-write heads access to the disk. Standard sizes include 8 inches, 5¼ inches, and 3½ inches. The larger sizes use a flexible jacket and the disk is exposed through an access slot. The smallest size has a rigid plastic case with a metal shutter to protect the disk and is sometimes called a flexi-disk.
A flippy is a single-sided 5¼-inch disk that has been altered so that data can be stored on both sides. The disk must be turned over (flipped) to use the second side.