A substance like tetraethyl lead which is added to gasoline to raise the octane number and reduce the gasoline's tendency to detonate, knock, or ping. In unleaded gasoline, tetraethyl lead is not used because of its environmental danger.
ANTI-KNOCK AGENT
Meaning of ANTI-KNOCK AGENT in English
English dictionary of automotive terms. Английский словарь автомобильных терминов. 2012