blowdown noun5 •Uprooting, overtopping, or bole breakage of trees by the wind; windthrow and windsnap. •The removal of liquid and solid hydrocarbons from a refinery vessel by the use of pressure. •(informal) An instance of blowing down with compressed air.Give these parts a blowdown with your air hose before you put them in the ultrasonic cleaning tank. •Cooling fluid discharged from a plant at the end of its cycle. •The action of aerodynamic forces to tend to cause a deflected control surface to return to its neutral position, or prevent the surface from deflecting past a certain point.At higher airspeeds, the 737's maximum rudder deflection is limited by blowdown, helping to prevent flight-control inputs from overstressing the aircraft's vertical stabilizer. formsblowdowns