sea turtle

from WordNet (r) 3.0 (2006)

sea turtle
    n 1: any of various large turtles with limbs modified into
         flippers; widely distributed in warm seas [syn: {sea
         turtle}, {marine turtle}]

from The Collaborative International Dictionary of English v.0.48

Sea turtle \Sea" tur"tle\ (Zool.)
   (a) 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.
   (b) The sea pigeon, or guillemot.
       [1913 Webster]