When someone says untrue and harmful remarks about another person in public the speaker may be guilty of what?

When someone makes untrue and harmful remarks about another person in public, the speaker may be guilty of defamation, which includes slander if the remarks are spoken. This can lead to legal consequences, as the affected individual may pursue a lawsuit for damages to their reputation. Additionally, such behavior can be considered a form of bullying or harassment, depending on the context and intent.