The written word form of defamation is Libel.
Defamation in general is a situation whereby a falsehood communication or statement is issued or passed which results to damaging reputation of a person, product, group of people, government religion or nation. When this form of communication can be proved as to have been written, published or can be available in the media, the in legal terms is referred to as a Libel and if it was just in form of a mere talk is termed as slender talk