to insult or cast aspersions on someone's reputation; to slur someone's character.
From be- (prefix) + slur (possibly from Low German or Scandinavian, meaning to defame or soil). The intensive prefix emphasizes thorough damage to reputation.
Slur has become much more famous recently for describing unclear speech or offensive language, but originally it just meant to soil or defame someone—the speech meaning came from 'sliding unclear words together'.
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