bad-mouth       
verb [ T ]  informal (also badmouth) uk/ˈbæd.maʊθ/ us/ˈbæd.maʊθ/
 苛刻地批评
to say bad things about someone to other people
  Her co-workers bad-mouthed her to her boss.
 You'll never hear him badmouthing an opponent.
 - More examples
 - You can promote your own qualities in a positive way without bad-mouthing others.
 - This woman is running around badmouthing a very successful scheme.
 - Instead of bad-mouthing those who do well, we should congratulate them for their achievements.
 - He is understood to be privately furious at the way he has been bad-mouthed.
 - In private party members are badmouthing their leader.