Reverse appending is a data enrichment process that involves adding missing or updated information to an existing database by matching and merging it with external data sources. Unlike traditional appending, which adds information to a database based on a known identifier, reverse appending uses the available data to identify and fill in any missing details. This method is particularly useful for businesses looking to enhance their customer data with additional contact information, demographics, or behavioral data. By utilizing reverse appending, companies can gain a more comprehensive understanding of their customers and improve their marketing and sales efforts.