WordNet (r) 3.0 (2006):

Marshals
    n 1: the United States' oldest federal law enforcement agency is
         responsible today for protecting the Federal Judiciary and
         transporting federal prisoners and protecting federal
         witnesses and managing assets seized from criminals and
         generally ensuring the effective operation of the federal
         judicial system [syn: United States Marshals Service, US
         Marshals Service, Marshals]