Drone.
Was taught to U.K. Services in the 70's (when the Army had the " Midge" ) to refer to an autonomous "clockwork mouse" device -hence incorporated into Royal Artillery Drone Troops.
Conversely an RPV /UMA/ UAV/RPA system implied that the mission was monitored and controlled from a ground station.
Thus ,politically and for very good reasons, it can then be claimed to be under human direction and discretion and thus avoid popular association with being seen as a "Robot Killer" or whatever.
This distinction has now been removed.