ace·to·ni·trile \|asə(ˌ)tōˈnī.trə̇l, əˌsēd.ō-, -ī.ˌtrēl, -īl\noun (-s) Etymology: International Scientific Vocabulary acet- + nitrile : the colorless liquid nitrile CH3CN of acetic acid usually made by dehydration of acetamide and used chiefly in organic synthesis and as a solvent — called also methyl cyanide