noun
: any of numerous snakes frequenting or inhabiting freshwaters and feeding largely on aquatic animals: as
a. : any of various snakes constituting a cosmopolitan genus ( Natrix ), being common in the eastern United States and sometimes a pest in fish hatcheries and rearing pools, and reaching a length of four feet
b. : an eastern Asian or Australian snake of the family Homalopsidae with valvular nostrils and often a compressed tail
c. : wart snake