Bumping.

If the arm is bent, with the elbow tucked into the side, a player can legally
• Bump an opponent when the ball is within five metres.
• Lean towards the opponent, pushing hard from the foot furthest from the opponent.
• Make contact with the shoulder and upper arm when an opponent is settled on one foot, so he is easier to unbalance.

The bumping player should:
• Keep his feet on the ground at all times.
• Only bump when an opponent does not have the ball.