unmitered

Unmitered describes a joint or corner that lacks a miter—the angled cut (typically 45 degrees) that allows two pieces to meet flush at a corner.

An unmitered frame has squared-off ends that butt together rather than meeting at a diagonal seam: The unmitered corners gave the cabinet a more rustic look.

In ecclesiastical contexts, unmitered means not wearing or entitled to wear a bishop's miter.