sea turtle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various large marine turtles of the families Cheloniidae and Dermochelyidae, including the green turtle, loggerhead turtle, Kemp's ridley, olive ridley, hawksbill, and leatherback, having flippers adapted for swimming and living chiefly in tropical and subtropical oceans.

from The Century Dictionary.

• noun The sea-pigeon, or black guillemot, Uria grylle. See cut under guillemot.
• noun Any marine chelonian; a sea-tortoise.

from the GNU version of the Collaborative International Dictionary of English.

• Any one of several very large species of chelonians having the feet converted into paddles, as the green turtle, hawkbill, loggerhead, and leatherback. They inhabit all warm seas.
• The sea pigeon, or guillemot.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any turtle that inhabits oceans.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of various large turtles with limbs modified into flippers; widely distributed in warm seas