Francis explored the Catholic commandment against "bearing false witness" during his Wednesday general audience.
He warned the faithful in a chilly St Peter's Square that "We all live by communicating, and we are continuously on the edge between truth and lies."
He repeated his complaint about gossip, saying it "kills because the tongue kills like a knife".
He warned: "Gossipers are terrorists because with their tongues they drop a bomb and then leave, and the bomb they drop destroys reputations everywhere."
"Don't forget: to gossip is to kill."
Francis frequently rails against gossip in the church and has urged the media in particular to guard against "fake news" and seek the truth.
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