Badmouth
ahd-5
transitive verb.
To criticize or disparage, often spitefully or unfairly.
Wiktionary, Creative Commons Attribution/Share-Alike License
verb.
To
criticize
or
malign
, especially unfairly or
spitefully
.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
verb.
speak unfavorably about