The same thing anybody would understand by the term. Did something gave you a different impression?

That there's a scientific proof that harm is being done by an action.

But harm is a moral term, and science is not about moral judgements. It can help inform them, but the guidelines for what is "harm" or "good" come from morality ultimately.

E.g. what is "good for society" is based on a value judgement / decision by said society based on its goals, what it wants to conserve or change, etc.

Science can tell you that X technique is more productive for example. But whether "more productivity" is desired is a matter of social values/priorities, not a scientific matter.