cromlech (n.)

"structure consisting of a large, flat, unhewn stone resting horizontally atop three or more upright ones," c. 1600, from Welsh, from crom, fem. of crwm "crooked, bent, concave" + llech "(flat) stone." Applied in Wales and Cornwall to what in Brittany is a dolmen; a cromlech there is part of a circle of standing stones.