A bit in a memory cache or virtual memory page that has been modified by the CPU, but not yet written back to storage.
Dirty data is inaccurate, incomplete or erroneous data, especially in a computer system or database.[1]
In reference to databases, this is data that contain errors. Unclean data can contain such mistakes as spelling or punctuation errors, incorrect data associated with a field, incomplete or outdated data, or even data that has been duplicated in the database.