If a robot is Autonomous, it is essentially a robot that does everything by itself without any interference from a human operator. To be a true robot, a machine must act completely by itself without a human operator (i.e. be autonomous). Antweights and other classes of fighting robots are not “true” robots, because they do not act by themselves.
Some robots that took part in Robot Wars™ did incorporate autonomous weapons, the most famous example being 101's spike that came out the front of the robot automatically when the opponent came within a certain distance of the sensor.
At recent Antweight World Series, a Minisumo competition has been held along side the Antweight fights. Minisumo robots ARE true robots, because they try to push each other out of the ring using sensors to detect where the other robot is and how best to attack it. In other words, they are Autonomous.