noun Classical Mythology.
Examples from the Web for pyriphlegethon
Pyriphlegethon is a stream of fire, which coils round the earth and flows into the depths of Tartarus.
This is that Pyriphlegethon, as the stream is called, which throws up jets of fire in different parts of the earth.
But souls of lighter guilt abide a year in Tartarus, and then drift out down the streams Cocytus and Pyriphlegethon.Letters on Literature|Andrew Lang