ratter

/ˈrætər/
noun
  1. A dog or other animal trained to catch and kill rats.
    • The terrier is an excellent ratter and keeps the barn free of rodents.
    • They adopted a ratter from the shelter to help with the mouse problem.
    • In the 1800s, ratters were often used in pits for sport.
  2. A person who catches rats professionally.
    • A good ratter knows all the hiding places of rats.
    • The city hired a ratter to control the rodent population in the sewers.
    • Old Tom worked as a ratter on the docks for twenty years.
  3. A person who informs on others; an informer.
    • He was known as a ratter after he told the police about the robbery.
    • No one trusts a ratter in this neighborhood.
    • The gang suspected a ratter in their midst and became paranoid.