According to Discover DEF, you can dilute DEF with water in a ratio of 1:10 and use it on your lawn.
As per trucknews.com, you can drain it on your lawn and you’ll have a nice new patch of grass there next summer.
Diesel Exhaust Fluid (DEF) is a non-hazardous solution, which is 32.5% urea and 67.5% de-ionized water. It is sprayed into the exhaust stream of diesel vehicles to break down dangerous NOx emissions into harmless nitrogen and water. This system is called Selective Catalytic Reduction (SCR) and can be found on 2010 and later model year trucks and many diesel pickups and SUVs.
DEF is not a fuel additive and never comes into contact with diesel. It is stored in a separate tank, typically with a blue filler cap.
Check out the Best Grass Fertilizing Tips from DIY.