Lashon hara
Lashon hara (or loshon horo, or loshon hora) (Hebrew: לשון הרע; "evil tongue") is the halakhic term for speech about a person or persons that is negative or harmful to them, even though it is true. It is speech that damages the person(s) that are talked about either emotionally or financially, or lowers them in the estimation of others.
Lashon hara differs from the more severe prohibition of hotzaat shem ra, "making a bad name," in that hotzaat shem ra consists of untrue statements.
Lashon hara is considered to be a very serious sin in the Jewish tradition. The communicator of lashon hara (which is included in rechilut) violates the Torah prohibition of lo telech rachil b'ameicha, translating to "thou shalt not go up and down as a talebearer among thy people" (Leviticus 19:16 KJV).