A 2- or higher-dimensional bounding box with orthogonal edges. Other than with AABBs, those edges are not aligned with the major world axes, but are aligned so that the resulting box fits the contained object optimally. That structure is reasonably easy to create and also allows for relatively quick collision detection. It is possible to create an OBB tree to perform those checks hierarchically.
The technique is applied in 3D graphics for very large objects built from several 100k faces.