The full, slightly more careful computer word for the same job as defrag: to change how files sit on a hard drive by gathering related pieces and putting them next to each other, so the machine can work more smoothly. The picture inside the word is “take away the fragments.” On an old spinning disk, a file is often not stored in one place; it is broken into pieces sitting in different spots, so the machine has to jump around to read it. To defragment the disk is to put those pieces of each file back together. People also stretch it, a little loosely, to mean “tidy a scattered mess,” but the home of the word is still disks. Though actually, on a modern SSD you usually should not defragment at all — the old need belongs to the older kind of disk. Tech talk; not a formal essay word. In speech, many people just say defrag.

磁碟重組（把硬碟裡散開的檔案碎片排回去）。台灣系統用語是「磁碟重組」；中國大陸較常說「磁盤碎片整理」。