(1) Making data more accurate and consistent; in other words, "cleaning it up". It refers to eliminating duplicate records, correcting misspellings and errors in names and addresses, ensuring consistent descriptions, punctuation, syntax and other content issues. Data scrubbing is often required when data from different databases are combined into one. See audio scrubbing and memory scrubbing.
(2) In a RAID disk system, monitoring and correcting parity byte errors that may occur (although infrequently) in order to keep the drives in synchronization.