abyssal

Adjective

abyssal (not comparable)

1. (archaic) Belonging to, or resembling, an abyss; unfathomable.
2. Of or belonging to the ocean depths, especially below 2000 metres (6500 ft): abyssal zone.
   • This "abyssal" life, typically in the form of strange tube-worms and microbes, is almost completely unknown to science.1994 November 15, The Canberra Times, Australian Captial Territory, page 11, column 6
   • "Ea", the beneficent god of earth and life, who dwelt in the abyssal waters, was shown with two streams running from his hands or shoulders[.]1998, John H. Roger, “Origins of the ancient constellations: I. The Mesopotamian traditions”, in Journal of the British Astronomy Association, volume 108, number 1, page 11, column 1
3. Pertaining to or occurring at excessive depths in the earth's crust; plutonic.
4. (figuratively) In the utter depths of despair; gloomy.
   • In an attempt to avoid sliding into incorrigible despair, I abandon such abyssal and existential pondering and investigate the artist behind the work.1998 August 11, Tharunka, Kensington, page 35, column 1