designating or of any of various synthetic fibers that resist combustion, made from long-chain polymers composed primarily of acrylonitrile modified by other polymers: used in making fabrics, carpets, etc.
See modacrylic in American Heritage Dictionary 4
(mŏdˌə-krĭlˈĭk)
noun
One of several synthetic, long-chain polymer textile fibers containing 35-85 percent acrylonitrile.