deceit: deliberate falsehood used to betray or cheat someone who trusts you
This word names deception with intent behind it. It is not an honest mistake or a harmless exaggeration; it is falsehood aimed at another person, meant to gain something at their expense or to bring them down. It runs from a lying tongue and a false witness, through a heart that quietly plots harm, to open betrayal of someone who had reason to trust you.
The Bible treats this as a moral fault, not merely a social flaw. It keeps company with violence and bloodshed, and the Psalms plead to be delivered from people marked by it. Because the deception is deliberate, the word carries a weight that softer terms like "mistake" or "misunderstanding" never do.
Most of the time the word covers deceit and treachery together: cheating and lying words, and, at its sharpest, the betrayal of a person who trusted the deceiver. A distinct group of verses narrows it to the marketplace, where it means fraud: the rigged scales and weighted measures that let a merchant rob a customer while looking honest.