Nouns

(n)smudge, spot, blot, daub, smear, smirch, slura blemish made by dirt“he had a smudge on his cheek”
(n)blot, smear, smirch, spot, stainan act that brings discredit to the person who does it“he made a huge blot on his copybook”

Verbs

(v)smirch, besmirchsmear so as to make dirty or stained
(v)defame, slander, smirch, asperse, denigrate, calumniate, smear, sully, besmirchcharge falsely or with malicious intent; attack the good name and reputation of someone“The journalists have defamed me!”, “The article in the paper sullied my reputation”