Phlegethon[fleg′i t̸hän, flej′-]
Phlegethon definition by Webster's New World
Origin: Classical Latin ; from Classical Greek Phlegethōn, origin, originally present participle of phlegethein, to blaze: for Indo-European base see flagrant
Phlegethon definition by American Heritage Dictionary
noun Greek Mythology
Origin: Middle English Flegeton, from Latin Phlegethōn, from Greek, from present participle of phlegethein, to blaze, variant of phlegein; see bhel-1 in Indo-European roots.