Drill-up refers to a navigation technique in interactive OLAP evaluations, the "climbing up" to the next higher hierarchical level of a dimension. This allows the data to be viewed at this higher aggregated level.
Online Analytical Processing (OLAP) is organized hierarchically. For example, the Delivery Address dimension at the top level may consist of the countries to which deliveries have been made. Below that is the level of regions, below that come the cities, then the postal codes, and then the actual addresses.
In an interactive evaluation, such as an ad hoc evaluation, the detailed figures can be aggregated to each hierarchical level of a participating dimension. The user drills up from a detailed view to view the same evaluation aggregated to the next higher level, e.g., to view the facts per region instead of per city.
The opposite term to drill-up is drill-down. The term drill-down is also related to the term drill-through.