ratter

Short definition from Wiktionary

Noun

1. 1
   Anything which catches rats, especially a dog trained to catch them; a rat terrier.
2. 2
   One who rats; a traitor; a deserter.
3. 3
   A pirate miner, a miner who digs out ore or paydirt clandestinely and runs

Proper noun

1. 1
   A surname.