Burl

A burl is an abnormal, tangled growth on a tree -- caused by stress, injury, or infection triggering a mass of dormant buds to grow in a disorganized clump rather than normal, straight-grained wood. Cut into lumber or veneer, that same chaos produces a wild, swirling grain pattern with no straight run anywhere in it, which is exactly why burl is prized for turning, veneer, and small decorative work despite (and largely because of) being far less structurally predictable than straight-grained wood from the same species.

Because the grain runs in every direction at once with no consistent long fibers to rely on, burl is notably weaker and more prone to cracking than ordinary wood from the same tree, and turning or working it often benefits from stabilizing with thin CA glue first, the same technique used on spalted or punky wood.