Synonyms for Besmirch (same or very similar meaning)
WordNet sense 1 (smear so as to make dirty or stained):
smirchWordNet sense 2 (charge falsely or with malicious intent; attack the good name and reputation of someone):
calumniate, defame, denigrate, slander, smear, sully, asperseFrom the ODE community, based on WordNetadd/edit