the action of damaging the good reputation of someone through slander or libel.
"she sued him for defamation" "Defamation" is a catch-all term for any statement that hurts someone's reputation. Written defamation is called "libel," and spoken defamation is called "slander." Defamation is not a crime, but it is a "tort" (a civil wrong, rather than a criminal wrong). A person who has been defamed can sue the person who did the defaming.
Defamation law tries to balance competing interests: On the one hand, people should not ruin others' lives by telling lies about them; but on the other hand, people should be able to speak freely without fear of litigation over every insult, disagreement, or mistake.