To flip - to move, push, or throw (something) with a sudden sharp movement. In your example there is a reference to lacrosse which is a team game, originally played by North American Indians, in which the ball is thrown, caught, and carried with a long-handled stick having a curved L-shaped or triangular frame at one end with a piece of shallow netting in the angle. I guess he flipped it like people do it in lacrosse game .
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