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]

U.S. Gazetteer Places (2000):

Cooter, MO -- U.S. city in Missouri
   Population (2000):    440
   Housing Units (2000): 200
   Land area (2000):     0.294810 sq. miles (0.763555 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.294810 sq. miles (0.763555 sq. km)
   FIPS code:            16336
   Located within:       Missouri (MO), FIPS 29
   Location:             36.045894 N, 89.810096 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Cooter, MO
    Cooter