The Collaborative International Dictionary of English v.0.48:

Abyss \A*byss"\, n. [L. abyssus a bottomless gulf, fr. Gr. ?
   bottomless; 'a priv. + ? depth, bottom.]
   1. A bottomless or unfathomed depth, gulf, or chasm; hence,
      any deep, immeasurable, and, specifically, hell, or the
      bottomless pit.
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            Ye powers and spirits of this nethermost abyss.
                                                  --Milton.
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            The throne is darkness, in the abyss of light.
                                                  --Dryden.
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   2. Infinite time; a vast intellectual or moral depth.
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            The abysses of metaphysical theology. --Macaulay.
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            In unfathomable abysses of disgrace.  --Burke.
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   3. (Her.) The center of an escutcheon.
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   Note: This word, in its leading uses, is associated with the
         cosmological notions of the Hebrews, having reference
         to a supposed illimitable mass of waters from which our
         earth sprung, and beneath whose profound depths the
         wicked were punished. --Encyc. Brit.
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WordNet (r) 3.0 (2006):

abyss
    n 1: a bottomless gulf or pit; any unfathomable (or apparently
         unfathomable) cavity or chasm or void extending below
         (often used figuratively) [syn: abyss, abysm]