What does 2 Peter 2:7 mean?

For if God didn’t spare angels when they sinned, but cast them down to Tartarus, and committed them to pits of darkness, to be reserved for judgment;

and didn’t spare the ancient world, but preserved Noah with seven others, a preacher of righteousness, when he brought a flood on the world of the ungodly;

and turning the cities of Sodom and Gomorrah into ashes, condemned them to destruction, having made them an example to those who would live in an ungodly way;

(for that righteous man dwelling among them, was tormented in his righteous soul from day to day with seeing and hearing lawless deeds):

the Lord knows how to deliver the godly out of temptation and to keep the unrighteous under punishment for the day of judgment;

but chiefly those who walk after the flesh in the lust of defilement, and despise authority. Daring, self-willed, they are not afraid to speak evil of dignitaries;