This “definition” just manufactures a fake reality. A machine gun fires more than one round with a single cycle of the trigger. With bump fire the rifle still only fires once with each pull of the trigger. Whether that pull is initiated by momentum or the muscles of a finger it still fires only one round per pull or cycle of the trigger.
I have a better counter-concept than that.
Even if it’s a machine gun we still have a god-given right to defend ourselves how we see fit.
While they are busy mashing the bump stock into the machine gun “rules” I’m busy freeing it all in accordance with the Constitution.