from The American Heritage® Dictionary of the English Language, 4th Edition
- n. One that catches or kills rats: Many terriers are good ratters.
- n. Slang One who betrays or deserts another.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Anything which catches rats, especially a dog trained to catch them; a rat terrier.
- n. One who rats; a traitor; a deserter.
from the GNU version of the Collaborative International Dictionary of English
- n. One who, or that which, rats, as one who deserts his party.
- n. Anything which catches rats; esp., a dog trained to catch rats; a rat terrier. See Terrier.
from The Century Dictionary and Cyclopedia
- n. One who catches rats; a rat-catcher.
- n. An animal which catches rats, as a terrier.
- n. One who rats, or becomes a renegade; also, a workman who renders himself obnoxious to a trades-union. See ratting, 2.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. any of several breeds of terrier developed to catch rats
- n. a disloyal person who betrays or deserts his cause or religion or political party or friend etc.
rat + -er (Wiktionary)