12. abussos -- boundless, bottomless
... deep, bottomless. From a (as a negative particle) and a variation of buthos; depthless,
ie (specially) (infernal) "abyss" -- deep, (bottomless) pit. see GREEK a ...
/greek/12.htm - 6kRevelation 9:1,2,11
And the fifth angel sounded, and I saw a star fall from heaven to the earth: and to him was given the key of the bottomless pit.
Nave's Topical Index—AKJV

Revelation 11:7
And when they shall have finished their testimony, the beast that ascends out of the bottomless pit shall make war against them, and shall overcome them, and kill them.
Nave's Topical Index—AKJV

Revelation 17:8
The beast that you saw was, and is not; and shall ascend out of the bottomless pit, and go into perdition: and they that dwell on the earth shall wonder, whose names were not written in the book of life from the foundation of the world, when they behold the beast that was, and is not, and yet is.
Nave's Topical Index—AKJV

Revelation 20:1,3
And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
Nave's Topical Index—AKJV