rat terrier vs ratter

rat terrier and ratter both are nouns.

Word	Noun	Adjective	Verb	Adverb
rat terrier	Yes	No	No	No
ratter	Yes	No	No	No

As nouns, rat terrier and ratter are synonyms defined as:

rat terrier and ratter: any of several breeds of terrier developed to catch rats

rat terrier (noun)	ratter (noun)
any of several breeds of terrier developed to catch rats	any of several breeds of terrier developed to catch rats
	a disloyal person who betrays or deserts his cause or religion or political party or friend etc.