What does abaddon mean?
The definition of abaddon
A*bad”don, n.
Etym: [Heb. abaddon destruction, abyss, fr. abad to be lost, to perish.]

1 The destroyer, or angel of the bottomless pit; — the same as Apollyon and Asmodeus.
2 Hell; the bottomless pit. [Poetic] In all her gates, Abaddon rues Thy bold attempt. Milton.