noun

• (chemical engineering) The removal of liquid and solid hydrocarbons from a refinery vessel by the use of pressure.
• (industrial engineering) Cooling fluid discharged from a plant at the end of its cycle.
• (forestry) Uprooting, overtopping, or bole breakage of trees by the wind; windthrow and windsnap.
• (aviation) 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."