n.1 a deep or seemingly bottomless chasm.
2 a an immeasurable depth (abyss of despair). b a catastrophic situation as contemplated or feared (his loss brought him a step nearer the abyss).
3 (prec. by the) primal chaos, hell.
Etymology: ME f. LL abyssus f. Gk abussos bottomless (as A-(1), bussos depth)