ˈstij(ē)ən adjective
Usage: often capitalized
Etymology: Latin stygi us stygian (from Greek stygios, from Styg-, Styx Styx, mythical stream considered to be the chief river of the subterranean world of the dead) + English -an
: of, relating to, or associated with the river Styx: as
a. : hellish , infernal , gloomy
b. : characteristic of death : deathly
upon those roseate lips a stygian hue — William Wordsworth
c. : inviolable
a stygian oath