The C.I.A., the F.B.I. and the White House may all agree that Russia was behind the hacking that interfered with the election. But that was of no import to the website Breitbart News, which dismissed reports on the intelligence assessment as left-wing fake news." Until now, that term had been widely understood to refer to fabricated news accounts that are meant to spread virally online. But conservative cable and radio personalities ... have appropriated the term and turned it against any news they see as hostile to their agenda. In defining "fake news" so broadly and seeking to dilute its meaning, they are capitalizing on the declining credibility of all purveyors of information. Journalists who work to separate fact from fiction see a dangerous conflation of stories that turn out to be wrong because of a legitimate misunderstanding with those whose clear intention is to deceive. A report, shared more than a million times on social media, that the pope had endorsed Mr. Trump was undeniably false. But was it "fake news" to report on data models that showed Hillary Clinton with overwhelming odds of winning the presidency? Are opinion articles fake if they cherry-pick facts to draw disputable conclusions? "Fake news was a term specifically about people who purposely fabricated stories for clicks and revenue," said David Mikkelson, the founder of Snopes, the myth-busting website. "Now it includes bad reporting, slanted journalism and outright propaganda. And I think we're doing a disservice to lump all those things together."