|Noah Webster's Dictionary|
(a.) Without a bottom; hence, fathomless; baseless; as, a bottomless abyss.
Int. Standard Bible Encyclopedia
bot'-um-les, (to phrear tes abussou, "the pit of the abyss," Revelation 9:1, 2 the King James Version): In the Revised Version (British and American), he abussos (always an adjective in classical authors = "bottomless") is uniformly rendered "the ABYSS" (which see) (Luke 8:31 Romans 10:7 Revelation 9:11; Revelation 11:7; Revelation 17:8; 20:1, 3).
Bottomless (9 Occurrences)
Luke 8:31 and they besought Him not to command them to be gone into the Bottomless Pit. (WEY DBY)
Revelation 9:1 And the fifth angel sounded, and I saw a star fall from heaven unto the earth: and to him was given the key of the bottomless pit. (KJV WEY WBS NAS RSV)
Revelation 9:2 And he opened the bottomless pit; and there arose a smoke out of the pit, as the smoke of a great furnace; and the sun and the air were darkened by reason of the smoke of the pit. (KJV WEY WBS NAS RSV)
Revelation 9:11 And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon. (KJV WEY WBS RSV)
Revelation 11:7 And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them. (KJV WEY WBS RSV)
Revelation 17:8 The beast that thou sawest 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. (KJV WEY WBS RSV)
Revelation 20:1 And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand. (KJV WEY WBS RSV)
Revelation 20:2 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. (WEY)
Revelation 20:3 And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season. (KJV WBS)