Oriented bounding box (OBB)
A box that rotates with its object, unlike the axis-aligned AABB — a tighter fit, but costlier to test.
An AABB has to grow every time its object turns, so a long thin stick on the diagonal gets a box full of air. An OBB (oriented bounding box) keeps its own orientation and so stays snug at any rotation.
The price is paid in the overlap test. Two arbitrarily rotated boxes cannot be compared axis by axis; you need the separating-axis theorem, which in 3D tests 15 candidate axes (6 face normals plus 9 edge-edge cross products). That is why you often see a cheap AABB in the broad phase and an OBB only when it really matters.