I. noun 1. a projecting part of a fortification built at an angle to the line of a wall, so as to allow defensive fire in several directions. 2. a natural rock formation resembling a man-made bastion. 3. an institution, place, or person strongly maintaining particular principles, attitudes, or activities • cricket’s last bastion of discrimination.
– origin mid 16th cent.: from French, from Italian bastione, from bastire ‘build’.