noun
1. : a joint formed in sheet-metal roofing by bending up the edge of a sheet and folding it downward over the turned-up edge of the next sheet
2. : a joint in a weathered course of masonry (as a coping or sill) between adjoining stones whose ends are cut higher than the surface of the weathering between
3. : a joint (as the carpometacarpal of the thumb) with saddle-shaped articular surfaces that are convex in one direction and concave in another and that permit movements in all directions except axial rotation