A system component that can communicate with and be added to or removed from a system or network and that is limited to data storage—including text, video, audio or image data—as its primary function (e.g., optical discs, external or removable hard drives, external or removable solid-state disk drives, magnetic or optical tapes, flash memory devices, flash memory cards, and other external or removable disks).
Sources:
NIST SP 800-53 Rev. 5

  A system component that can be inserted into and removed from a system and that is used to store information or data (e.g., text, video, audio, and/or image data). Such components are typically implemented on magnetic, optical, or solid-state devices (e.g., compact/digital video disks, flash/thumb drives, external solid-state drives, external hard disk drives, flash memory cards/drives that contain nonvolatile memory).
Sources:
NIST SP 800-171r3