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Webster 1913 Edition

(răt′tẽr)

Noun.

One who, or that which, rats, as one who deserts his party.

Anything which catches rats; esp., a dog trained to catch rats; a rat terrier. See

See also: rätter

ratter ‎(plural ratters)

Anything which catches rats, especially a dog trained to catch them; a rat terrier.
One who rats; a traitor; a deserter.