one of the rivers of hell, according to the theology of the poets. It has its name ἀπὸ τῷ κυκυτίῳ, from groaning and lamenting. Hence Milton,

Cocytus nam'd of lamentation loud, Heard on the rueful stream.

It was a branch of the river Styx; and flowed, according to Horace, with a dull and languid stream.