[adj] so deep as to be unmeasurable; unfathomable; "the abyssal depths of the ocean"
[adj] very great; limitless; "abysmal misery"; "abysmal stupidity"
\A*bys"mal\, a. Pertaining to, or resembling, an abyss; bottomless; unending; profound. Geology gives one the same abysmal extent of time that astronomy does of space. --Carlyle.