Noun
A flat-bottomed river barge or coasting vessel.
Source: Webster's dictionaryThe policemen who come to Alex's rescue turn out to be none other than Dim and former gang rival Billyboy. Source: Internet
Early on in the story, Alex and his droogs battle Billyboy and his droogs, which ends abruptly when the police arrive. Source: Internet
Later, after Alex is released from prison, Billyboy (along with Dim, who like Billyboy has become a police officer) rescue Alex from a mob, then subsequently beat him, in a location out of town. Source: Internet