abyssal

Definitions of abyssal
1

adj relating to ocean depths from 2000 to 5000 meters

adj resembling an abyss in depth; so deep as to be unmeasurable

“the abyssal depths of the ocean”
Synonyms:
abysmal, unfathomable
deep
having great spatial extension or penetration downward or inward from an outer surface or backward or laterally or outward from a center; sometimes used in combination

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