1. A fortified structure used to furnish protection against enemy attack in frontier areas, usually at a location of strategic importance; often square or polygonal in plan; typically constructed of hewn timbers having dovetailed notches at the corners to provide strong rigid joints; commonly, an overhanging upper story; often masonry walls on the ground story with log construction above, or entirely of log construction; frequently, a
pyramidal roof; usually a few small windows with heavy shutters;
loophole openings through the walls permit the firing of guns over a wide range of angles.