Passage: Diesel exhaust fluid (DEF)  is an aqueous urea solution made with 32.5% urea and 67.5% deionized water. It is standardised as AUS 32 (aqueous urea solution) in ISO 22241. DEF is a consumable in selective catalytic reduction (SCR) that lowers NOx concentration in the diesel exhaust emissions from diesel engines.The German Association of the Automotive Industry (VDA) registered the trademark AdBlue for AUS 32.

Question: What does DEF stand for?
Diesel exhaust fluid