Entry 1 sense Webster, 1913 Stygian /(stĭj"ĭ*an)/ · Styg·i·an · IPA /ˈstɪd͡ʒ.i.ən/ 01 a. Of or pertaining to the river Styx; hence, hellish; infernal. See Styx. 1. Of or pertaining to the river Styx; hence, hellish; infernal. See Styx. See: Styx “At that so sudden blaze, the Stygian throng Bent their aspect.” — Milton.