A "dirty read" occurs in database management when a transaction reads data that has been modified by another transaction but not yet committed. This means that the reading transaction may access information that could change or be rolled back, leading to potential inconsistencies. For example, if Transaction A updates a record but hasn't committed the change, and Transaction B reads that record, Transaction B is performing a dirty read. If Transaction A later rolls back its changes, the data that Transaction B read would be incorrect, potentially causing errors in applications relying on that data.