Evil…doesn’t mean doing things that have bad consequences for people. It means private thoughts and actions that are not to “the Christian majority’s” private liking.

Evil is the absence of God.

Evil is nothing but a word, an objectification where no objectification is necessary. Cast aside this notion of some external agency as the source of inconceivable inhumanity - the sad truth is our possession of an innate proclivity towards indifference, towards deliberate denial of mercy, towards disengaging all that is moral within us.
But if that is too dire , let's call it evil. And paint it with fire and venom.

Evil is ignorance.

Evil was defined as the use of power to destroy the spiritual growth of others for the purpose of defending and preserving the integrity of our own sick selves. In short, it is scapegoating. We scapegoat not the strong but the weak. For the evil to so misuse their power, they must have the power to use in the first place. They must have some kind of dominion over their victims. The most common relationship of dominion is that of parent over child. Children are weak, defenseless, and trapped in relation to their parents. They are born in thrall to their parents ... They are simply not free or powerful enough to escape.

Evil is movement towards void.

Evil is something that, when you see it, when you know it, it's intimate. It's almost sensual. That is why people who have been tortured know it by instinct. They don't need to be told what it is, and they may have a very hard time putting it into words. ... That's the nature of the phenomenon. It's hard to put into words.

Evil," the priest said, after he had settled comfortably into Barrent's best chair, "is that force within us which inspires men to acts of strength and endurance. The worship of Evil is essentially the worship of oneself, and therefore the only true worship. The self which one worships is the ideal social being; the man content in his niche in society, yet ready to grasp any opportunity for advancement; the man who meets death with dignity, who kills without the demeaning vice of pity. Evil is cruel, since it is a true reflection of the uncaring and insensate universe. Evil is eternal and unchanging, although it comes to us in the many forms of protean life.

Evil is the chronic malady of the universe, and checked in one place, breaks forth in another.

Evil is the vulgar lover who loves the body rather than the soul, inasmuch as he is not even stable, because he loves a thing which is in itself unstable, and therefore when the bloom of youth which he was desiring is over, he takes wing and flies away, in spite of all his words and promises; whereas the love of the noble disposition is life-long, for it becomes one with the everlasting.

Evil is whatever distracts.

Evil means, he insisted, corrupt and degrade not only the purposes for which they are undertaken but also the persons who stoop to such means. Overcoming the urge to resort to such means is hardest when one aims to rectify past injustices. It is because ‘hate the sin and not the sinner’ is a precept so rarely practiced that the poison of hatred spreads in the world.

Evil is a by-product of forgetfulness, laziness, or distraction: it arises when we lose sight of our true aim in life

Evil, then consists essentially in the choice of what is lower in preference to what is higher.