Sentence:  And the poor "spailpin fanach" running like the devil, his clothes tearing on briars and brambles, and his feet soaking and dirty water running out of his boots, and the three big buckos giving him every dirty look if he <WSD>fustered</WSD> or faltered, looks that'd sour milk or peel paint from walls. 
Meaning of the word marked with <WSD> tags:  To fumble; to work clumsily.