The Collaborative International Dictionary of English v.0.48:
Cooter \Coot"er\ (-[~e]r), n. (Zool.) (a) A fresh-water tortoise (Pseudemus concinna) of Florida. (b) The box tortoise. [1913 Webster]WordNet (r) 3.0 (2006):
cooter n 1: large river turtle of the southern United States and northern Mexico [syn: cooter, river cooter, Pseudemys concinna]