Noun
(mythology, literature) A mytheme or trope in which the hero embarks on a journey to the underworld.
(by extension, humorous) Any journey downwards or fall.
A retreat, especially a military one.
Antonym: anabasis
A journey from the interior of a country to the coast.
(rare) The presence of downward (drainage or katabatic) winds.
Source: en.wiktionary.org