"Do not slander a slave to his master, or he will curse you and you will be found guilty."
This is the Hebrew word lasan, which means slander. The English definition of slander is uttering false charges or misrepresentations about a person.
This is the Hebrew word ebed, which means servant or slave. The idea is that Solomon is using a hyperbole to get across the point that false charges or misrepresentations are not profitable against anyone, even those who would seem to be okay to make slanderous charges about. Many would expect that it is okay to make misrepresentations about a slave or servant during biblical times since they had no standing, but even this class of people are vigorously protected when they are slandered.
But remember that this is not the kind of slander that Solomon is aiming at having us stop. He is using hyperbole to scream: Stop making false charges or misrepresentations about anyone! For if a person will curse those who slander their slave, what will they do when you slander people who are not that low on the priority scale.
Be very careful about slander. Most everyone likes to hear it, but it clearly is destructive. Do not get involved in misrepresenting a person, a product, a place. Even if you had a bad experience, it does not mean that the person is that way as the general rule.
This is one of the typical ways that we slander people. We take our experience with people and magnify that into the whole of their life. Especially if they were rude or curt or lacking integrity, we can so easily jump to conclusions about a person and make a small thing in their life the whole of their life.
We, of all people, should make sure that we do not pre-judge people or too quickly believe what others tell us or focus on a person's weaknesses rather than their whole life.
Do not make false charges or misrepresent; it is easy to do but will only cause people to mistrust you.