Drone
Definition
An unmanned aircraft — most commonly a quadcopter — that stays aloft and maneuvers using spinning rotors, sensors, and onboard stabilization.
Technical definition
An unmanned aerial vehicle whose flight is maintained by rotor thrust balanced against weight, with attitude controlled by varying individual rotor speeds. MEMS gyroscopes and accelerometers feed a control loop running hundreds of times per second to hold stable hover.
Example
A quadcopter hovers when its four rotors together produce thrust equal to its weight. To move forward, it tilts slightly so part of the thrust points horizontally — the same vector-component idea as pushing a swing at an angle.
Drones do not fly 'because of Bernoulli' alone or by any single trick — lift comes from rotors accelerating air downward (Newton's third law), and stability comes from active electronic control, not from the airframe's shape. Turn off the stabilization software and most quadcopters cannot stay airborne.