Term used for nitrous oxide. Somewhat incorrect since NOS is a company that produces nitrous oxide, also the company is pronounced as spelled...N, O, S; opposed to the common pronounciation similar to the word "gnaw" except with an "s" sound at the end. This term was put into play mainly by the movie series of "The Fast and The Furious". Most people that say the "gnaws" pronounciation of this have no clue what they are talking about with cars and are what you would consider "wanna be's"
Im going to go say NOS (gnaws pronounciation) cause it was in a movie.