Bible Dictionary · D
Deep
Used to denote (1) the grave or the abyss (Rom 10:7; Luke 8:31); (2) the deepest part of the sea (Ps 69:15); (3) the chaos mentioned in Gen 1:2; (Gen 4:1–26) the bottomless pit, hell (Rev 9:1, Rev 9:2; Rev 11:7; Rev 20:13).
From Easton’s Bible Dictionary (1897), by Matthew George Easton.