grass snake

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

• noun Any of several greenish nonvenomous snakes, especially Opheodrys vernalis of eastern North America or Natrix natrix of Europe.

from The Century Dictionary.

• noun Same as ringed snake (which see, under snake).
• noun In the United States, the green-snake.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A nonvenomous snake, Natrix natrix, native to Europe, with a yellow collar.
• noun A greenish nonvenomous snake, Opheodrys vernalis, of North America.

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

• noun any of numerous nonvenomous longitudinally-striped viviparous North American and Central American snakes
• noun harmless European snake with a bright yellow collar; common in England
• noun either of two North American chiefly insectivorous snakes that are green in color