Soiling, tarnishing.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (verb) (v. impers.) (verb, impersonal)

Usage examples:

He, remaining as beautiful as when at twenty- one he had inspired the painter with a masterpiece, walks in the ways of men, sullying his soul, whose bodily reflection records neither his age nor his sins.
- Oscar Wilde A Critical Study by Arthur Ransome
After a while Bianca became aware that tongues were a- wag in Venice, sullying her name with foul calumnies.
- Terribly Intimate Portraits by Noël Coward
Drinking the dregs of a cup such as I had never considered it possible for me to taste, I got so far as to believe that her eyes would yet flash upon me from beneath some of the tattered shawls I saw sullying the forms of the young girls upon which I hourly stumbled.
- A Strange Disappearance by Anna Katharine Green