A fuzzy backup is a secondary (or backup

Backup

In information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....

) copy of data file(s) or directories that were in one state when the backup started, but in a different state by the time the backup completed. This may result in the backup copy being unusable because of the data inconsistencies

Data consistency

Data consistency summarizes the validity, accuracy, usability and integrity of related data between applications and across an IT enterprise. This ensures that each user observes a consistent view of the data, including visible changes made by the user's own transactions and transactions of other...

. Although the backup process might have seemed successful, the resultant copies of the files or directories could be useless because a restore would yield inconsistent and unusable data.