Sentence:  But poverty's scourge is fiercest below $1.25 (the average of the 15 poorest countries' own poverty lines, measured in 2005 dollars and adjusted for differences in purchasing power): people below that level live lives that are poor, <WSD>nasty</WSD>, brutish and short. 
Meaning of the word marked with <WSD> tags:  Dirty, filthy. (from 14th c.)