Sentence:  Henry Mayhew, the nineteenth-century chronicler of London's underworld, described the frenzied activity of one <WSD>ratting</WSD> contest. A terrier — the best of ratting dogs — was placed into a pit with 50 rats. 
Meaning of the word marked with <WSD> tags:  The blood sport of setting a dog upon rats confined in a pit to see how many he will kill in a given time.