The Collaborative International Dictionary of English v.0.48:

Abaddon \A*bad"don\ ([.a]*b[a^]d"d[u^]n), n. [Heb. [=a]badd[=o]n
   destruction, abyss, fr. [=a]bad to be lost, to perish.]
   1. The destroyer, or angel of the bottomless pit; -- the same
      as Apollyon and Asmodeus.
      [1913 Webster]

   2. Hell; the bottomless pit. [Poetic]
      [1913 Webster]

            In all her gates, Abaddon rues
            Thy bold attempt.                     --Milton.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "Abaddon":
   Aeshma, Angra Mainyu, Apollyon, Azazel, Beelzebub, Belial, Eblis,
   Gehenna, Hades, Lilith, Mephisto, Mephistopheles, Naraka,
   Pandemonium, Putana, Sammael, Shaitan, Sheol, Tophet, avichi, hell,
   infernal regions, inferno, jahannan, limbo, lower world,
   nether world, perdition, place of torment, purgatory, shades below,
   the abyss, the bottomless pit, the grave, the pit, underworld



Easton's 1897 Bible Dictionary:

Abaddon
   destruction, the Hebrew name (equivalent to the Greek Apollyon,
   i.e., destroyer) of "the angel of the bottomless pit" (Rev.
   9:11). It is rendered "destruction" in Job 28:22; 31:12; 26:6;
   Prov. 15:11; 27:20. In the last three of these passages the
   Revised Version retains the word "Abaddon." We may regard this
   word as a personification of the idea of destruction, or as
   sheol, the realm of the dead.


Hitchcock's Bible Names Dictionary (late 1800's):

Abaddon, the destroyer