acrylonitrile Syllabification: (ac·ry·lo·ni·trile)Pronunciation: /ˌakrəlōˈnītril, -trēl, -trīl/Definition of acrylonitrile noun Chemistry a pungent, toxic liquid, used in making artificial fibers and other polymers. The nitrile of acrylic acid: chemical formula: CH2=CHCN acrylonitrile in other Oxford dictionaries Definition of acrylonitrile in the British & World English dictionary