rat snake

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several nonvenomous snakes of the genus Elaphe that eat rats and other rodents.

from The Century Dictionary.

• noun A colubrine serpent of the genus Ptyas, P. mucosus, a native of India, Ceylon, etc., attaining a length of 7 feet, frequently entering houses. Some similar snakes are also called by the same name.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of various nonvenomous rodent-eating snakes of North America and Asia