oceanic_abyss
1. [ noun ] (geology,geography) a long steep-sided depression in the ocean floor
Synonyms: deep trench
Related terms: natural_depression japan_trench bougainville_trench nares_deep atacama_trench
2. [ noun ] (geography) literary term for an ocean
Synonyms: deep
Examples:

"denizens of the deep"

Related terms: body_of_water ocean main
Similar spelling:   oceanic_bird
  oceanic_bonito