The "South African Drill" is an illegal form of throw in the discus. In that drill, quite often done in warm up, one foot is outside the circle. Please see youtube video at: https://www.youtube.com/watch?v=60Fyun_Szw4

Please remember that Rule 6-5-9c indicates that after starting the attempt, the competitor cannot touch any surface outside the circle during the throw. The throw starts with the first motion of the athlete with the implement being thrown. If the athlete winds up while one foot is outside of the circle a foul will be called.