Sentence:  She was a living doll and no mistake - the blue-black bang , the wide cheekbones , olive flushed , that betrayed the Cherokee strain in her Midwestern lineage , and the mouth whose only <WSD>fault</WSD> , in the novelist 's carping phrase , was that the lower lip was a trifle too voluptuous . 
Meaning of the word marked with <WSD> tags:  an imperfection in an object or machine