Meaning

1. A rat, medium-sized rodent belonging to the genus Rattus, or of certain other genera in the family Muridae.
2. (informal) Any of the numerous, fairly large members of several rodent families that resemble true rats in appearance.
3. (informal) A traitor; a scoundrel; a quisling.
4. (informal) An informant or snitch.
5. (informal) An urchin.
6. (informal) A pauper; undesirable commoner.
7. (slang) A watch.