1. The allocation of a file in noncontiguoug sectors on a floppy or hard disk. Fragmentation occues because of multiple file delections and write operations. File gramentattion can seriously reduce disk efficiency, because a disk drive's rad/write head must travel longer distances to retreive a file that's scattered all over the disk. Defragmenting can improve disk efficiency by as much as 50 percent by rewriting files so that they are placed in contiguous clusters. See defragmentation. From QUECID