(Spor) A punching bag (US) or punch-bag (UK) is a sturdy bag designed to be repeatedly punched, for use in physical exercise or stress relief in order to improve one of three areas: physical strength, aerobic fitness, or punching technique
{i} stuffed bag that is made to be punched with the fists as training or as an exercise (particularly used by boxers)
A punchbag is a heavy leather bag, filled with a firm material, that hangs on a rope. Punchbags are used by boxers and other sportsmen for exercise and training