abyssal
1. [ adjective ] relating to ocean depths from 2000 to 5000 meters
Related terms: abyssal_zone
2. [ adjective ] so deep as to be unmeasurable; unfathomable
Synonyms: unfathomable abysmal
Examples:

"the abyssal depths of the ocean"

Related terms: deep
Similar spelling:   abseil
  absolve
  absolver
  absolved
  absolute
  abseiler
  abaxial