Abaddon

Destruction, the Hebrew name (equivalent to the Greek Apollyon, i.e., destroyer) of "the angel of the bottomless pit" (Revelation 9:11). It is rendered "destruction" in Job 28:22; 31:12; 26:6; Proverbs 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.

Source: Easton's Bible Dictionary
Abaddon

ABAD'DON, n. Heb. Ch. Syr. Sam. to be lost, or destroyed, to perish.

1. The destroyer, or angel of the bottomless pit. Rev. ix.
2. The bottomless pit.
Source: King James Dictionary