Plain English Meaning
It is the step-by-step order for handling the airplane: point the nose where you want it, set the wings level or banked as needed, adjust the power, trim out the pressure on the controls, then check the instruments to make sure it worked.
Full Definition
The recommended order in which a pilot uses the flight controls to fly the airplane: first establish the desired pitch and bank attitude with the elevator and ailerons, then add the necessary power with the throttle, trim off control pressures, and finally the instruments to confirm the airplane is doing what was .