'Bottomless' in the Bible

The fifth angel blew his trumpet; and I saw a Star which had fallen from Heaven to the earth; and to him was given the key of the depths of the bottomless pit,

and he opened the depths of the bottomless pit. And smoke came up out of the pit resembling the smoke of a vast furnace, so that the sun was darkened, and the air also, by reason of the smoke of the pit.

The locusts had a king over them--the angel of the bottomless pit, whose name in Hebrew is 'Abaddon,' while in the Greek he is called 'Apollyon.'

"And when they have fully delivered their testimony, the Wild Beast which is to rise out of the bottomless pit will make war upon them and overcome them and kill them.

"The Wild Beast which you have seen was, and is not, and yet is destined to re-ascend, before long, out of the bottomless pit and go his way into perdition. And the inhabitants of the earth will be filled with amazement--all whose names are not in the Book of Life, having been recorded there ever since the creation of the world--when they see the Wild Beast: because he was, and is not, and yet is to come.

Then I saw an angel coming down from Heaven, having the key of the bottomless pit, and upon his arm he carried a great chain.

He laid hold of the Dragon--the ancient serpent--who is the Devil and the Adversary, and bound him for a thousand years, and hurled him into the bottomless pit.