terrapin

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various North American aquatic turtles of the family Emydiolae, especially the genus Malaclemys, which includes the diamondback terrapin.

Century Dictionary and Cyclopedia

1. n. One of several different freshwater or tide-water tortoises of the family Emydidæ; specifically, in the United States, the diamond-back, Malaclemmys or Malacoclemmys palustris, of the Atlantic coast from New York to Texas, famous among epicures. See diamond-backed turtle (under diamond-backed), and Malaclemmys. In trade use the sexes are distinguished as bull and cow, and small ones as little bulls and heifers respectively. Those under 5 or 6 inches in total length of the under shell are termed cullings, of which it takes from 18 to 24 or more to make a “dozen.” Those of 6 inches and more are counts or counters, of 12 to the dozen. Only the cows reach 6½ to 7 inches in this measurement; these are known to dealers as full counts, and are especially valuable because they usually contain eggs; the bulls are tougher as well as smaller, and of less market value.
2. n. Some other tortoise or turtle: as, the elephant terrapin of the Galapagos.
3. n. A dish made of the diamond-back.

Wiktionary

1. n. Any of several North American turtles, of the family Emydidae, that live in fresh or brackish water.

GNU Webster's 1913

1. n. (Zoöl.) Any one of numerous species of tortoises living in fresh and brackish waters. Many of them are valued for food.

WordNet 3.0

1. n. any of various edible North American web-footed turtles living in fresh or brackish water