What is the definition of "Partition Pruning"?

From the Oracle 11 documentation


Oracle Database explicitly recognizes partitions and subpartitions.
It then optimizes SQL statements to mark the partitions or subpartitions that need to be accessed and eliminates (prunes) unnecessary partitions or subpartitions from access by those SQL statements.

In other words, partition pruning is the skipping of unnecessary index and data partitions or subpartitions in a query.

See also my post about the difference between dynamic and static pruning