cast down to tartarus ("hell") - 2 Peter 2:4

[sven]

I think this explanation from the appendix of The Kingdom Interlinear Translation of the GREEK SCRIPTURES is not that bad, maybe it helps anybody:

"Tartarus" is found only in 2 Peter 2:4. It is included in the Greek verb tartaroō, and so in rendering the verb, the phrase "by throwing them into Tartarus" has been used. In the Iliad, by the ancient poet Homer, the word tartaros denotes an underground prison as far below Hades as the earth is below heaven. Those confined in it were not human souls, but the lesser gods, spirits, namely, Cronus and the other Titans who had rebelled against Zeus (Jupiter). It was the prison established by the mythological gods for the spirits whom they had driven from the celestial regions, and it was below the Hades where human souls were thought to be confined at death. In mythology tartaros was the lowest of the lower regions and a place of darkness. It enveloped all the underworld just as the heavens enveloped all that was above the earth. Therefore, in pagan Greek mythology tartaros was reputed to be a place for confining, not human souls, but Titan spirits, and a place of darkness and abasement.

The use of tartaros in such places as Job 40:20; 41:23, 24 in the Septuagint makes it plain that the word was used to signify a low place, yes, the "lowest part" of the abyss. The inspired Scriptures do not consign any human souls to tartaros but consign there only spirit creatures, namely, "the angels that sinned." Their being cast into tartaros denotes the deepest abasement for them while they are still living. This serves as punishment for their sin of rebellion against the Most High God. The apostle Peter associates darkness with their low condition, saying that God "delivered them to pits of dense darkness to be reserved for judgment." – 2 Peter 2:4.

The pagans in their mythological traditions concerning Cronus and the rebellious Titan gods presented a distorted view regarding the abasement of rebellious spirits. In contrast, Peter's use of the verb tartaroō, "cast into Tartarus", does not signify that the "angels that sinned" were cast into the pagan mythological Tartarus, but that they were abased by the Almighty God from their heavenly place and privileges and were delivered over to a condition of deepest mental darkness respecting God's bright purposes.

Also, they had only a dark outlook as to their own eventuality, which the scriptures show is everlasting destruction along with their ruler, Satan the Devil. Therefore Tartarus denotes the lowest condition of abasement for those rebellious angels. In the inspired Scriptures, Tartarus bears no relationship to Hades, which is the common grave of the human dead. The sinful angels and the dead human souls are not associated together in tartaros as a place of eternal conscious torment of creatures. Tartarus will pass away when the Supreme Judge destroys the rebellious angels presently in that condition of abasement.