Data which enters an information system in a format or with values which the system has not been programmed to handle. Using various assumptions, such data can be "cleaned" or filtered in order to make it usable to the software.
Dirty Data is a term used by IT practitioners when creating data capture forms. Dirty Data is data that is misleading, incorrect or without generalized formatting, contains spelling or punctuation error, (see: transcription error), data that is inputted in a wrong field or duplicate data. It is commonly prevented using input masks or validation rules, however, completely removing the Dirty Data from a database is in some cases impossible.