Master Data Management (MDM) aims to provide a single point of reference for an organisation's slow-moving but critical data. MDM does not give precedence to fast-moving / transaction data.
A master data management tool can be used to support master data management by removing duplicates, standardizing data (mass maintaining), and incorporating rules to eliminate incorrect data from entering the system in order to create an authoritative source of master data.
Here is the Wikipedia article for MDM.