Which term describes a statement that is untrue and damages someone's reputation?

The term that best describes a statement that is untrue and damages someone's reputation is defamation. Defamation is a legal term that encompasses any false statement about a person that causes harm to their reputation. It can cover both spoken and written statements, with slander specifically referring to spoken defamation and libel to written or published defamation.

Defamation as a broader category includes both slander and libel, making it the most comprehensive term for understanding how false statements can affect an individual's reputation. Malpractice, on the other hand, pertains to negligence or misconduct by professionals in their fields, which is not directly related to the damage of reputation resulting from false statements.