In judiciary, what is the meaning of defamation linguistically and legally (in Islamic law)?

Linguistically, "tash'heer" (defamation/publicizing) means to declare, clarify, and not conceal. Religiously, it means not concealing the one who openly commits a sin or an evil, either to warn others against him or to discipline him. It is permissible to publicize (or expose) someone who openly commits a sin because he does not refrain from doing so, and this is not considered backbiting against him, for whoever casts off the cloak of modesty has no immunity from backbiting.