Nitrous is a slang term for nitrous oxide (N2O) also sometimes referred to as NOS. This misnomer most likely came about due to the abbreviation of the company name Nitrous Oxide Systems (NOS) - who were amongst those pioneers to develop systems for automotive performance use. More recently, the term was used prominently in the film The Fast and the Furious, and not surprisingly, shortly after the film's release, various automotive newsgroups and forums featured unprecedented numbers of inquiries about "NOS" and how to install and use it.

Nitrous oxide is an oxidizing agent used to increase an engine's power output by allowing more fuel (usually gasoline or alcohol) to be burnt at a faster rate