[con.cus.sion] n [ME concussioun, fr. MF or L; MF concussion, fr. L concussion-, concussio, fr. concutere to shake violently, fr. com- + quatere to shake] (14c) 1 a: a stunning, damaging, or shattering effect from a hard blow; esp: a jarring injury of the brain resulting in disturbance of cerebral function b: a hard blow or collision
2: agitation, shaking -- con.cus.sive adj