To limit or reduce the extent of one dataset by the extents or boundary of another.
A clip operation in GIS seeks to limit or reduce the extent of one dataset by the extents or boundary of another and usually results in the creation of a new, smaller dataset. For example one might trim a river layer for an entire continent using just one country's border, or cut out a specific area of interest from a large raster image.
Clip can apply to both vector and raster data. While it typically preserves the area of intersect between the two datasets, depending on implementation it may discard this area - also known as an Erase.