abyssal

UK: /əˈbɪsəl/ US: /əˈbɪsəl/ ,(ə bis′əl)

WordReference Random House Learner's Dictionary of American English © 2025

a•byss•al /əˈbɪsəl/   adj. 

1. of or like an abyss;
   too great to be measured or understood.
2. Ecology, Oceanography of or concerning the deepest areas of the ocean.

WordReference Random House Unabridged Dictionary of American English © 2025

a•byss•al  (ə bis′əl), adj. 

1. of or like an abyss;
   immeasurable;
   unfathomable.
2. Ecology, Oceanography of or pertaining to the biogeographic zone of the ocean bottom between the bathyal and hadal zones: from depths of approximately 13,000 to 21,000 ft. (4000 to 6500 m).

• Medieval Latin abyssālis. See abyss, -al¹
• 1685–95

Collins Concise English Dictionary © HarperCollins Publishers::

abyssal / əˈbɪsəl/ adjective

1. of or belonging to the ocean depths, esp below 2000 metres (6500 feet): abyssal zone
2. another word for plutonic