Avernus, a deep lake in Italy, near Naples, 1½ m. in circumference, occupying the crater of an extinct volcano, at one time surrounded by a dark wood, and conceived, from its gloomy appearance, as well as from the mephitic vapours it exhaled, to be the entrance to the infernal world, and identified with it.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Avenzo`ar * Aver`roës