A semiaquatic pit viper (Agkistrodon piscivorus) of lowlands and swampy regions of the southern United States. Also called cottonmouth.(noun)
Any of various similar but harmless water snakes.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.