WordNet sense 1 (a mark or flaw that spoils the appearance of something (especially on a person's body)):

defect, mar, defect

WordNet sense 2 (mar or spoil the appearance of):

deface, disfigure

WordNet sense 3 (mar or impair with a flaw):

spot

WordNet sense 4 (add a flaw or blemish to; make imperfect or defective):

flaw