defragment
verb [ I or T ] uk/ˌdiː.fræɡˈment/ us/ˌdiːˈfræɡ.ment/ (informal defrag, uk/ˌdiːˈfræɡ/ us/ˌdiːˈfræɡ/ -gg-)
（计算机）整理磁盘碎片
to make a computer organize its files and free space so that it can operate more quickly
Defragment your computer overnight. 让你的电脑在夜间整理磁盘碎片。