The Collaborative International Dictionary of English v.0.48:

Turtle \Tur"tle\, n. [Probably the same word as the word
   preceding, and substituted (probably by sailors) for the
   Spanish or Portuguese name; cf. Sp. tortuga tortoise, turtle,
   Pg. tartaruga, also F. tortue, and E. tortoise.]
   [1913 Webster]
   [1913 Webster]
   1. (Zool.) Any one of the numerous species of Testudinata,
      especially a sea turtle, or chelonian.
      [1913 Webster]

   Note: In the United States the land and fresh-water tortoises
         are also called turtles.
         [1913 Webster]

   2. (Printing) The curved plate in which the form is held in a
      type-revolving cylinder press.
      [1913 Webster]

   Alligator turtle, Box turtle, etc. See under Alligator,
      Box, etc.

   green turtle (Zool.), a marine turtle of the genus
      Chelonia, having usually a smooth greenish or
      olive-colored shell. It is highly valued for the delicacy
      of its flesh, which is used especially for turtle soup.
      Two distinct species or varieties are known; one of which
      (Chelonia Midas) inhabits the warm part of the Atlantic
      Ocean, and sometimes weighs eight hundred pounds or more;
      the other (Chelonia virgata) inhabits the Pacific Ocean.
      Both species are similar in habits and feed principally on
      seaweed and other marine plants, especially the turtle
      grass.

   Turtle cowrie (Zool.), a large, handsome cowrie (Cypraea
      testudinaria); the turtle-shell; so called because of its
      fancied resemblance to a tortoise in color and form.

   Turtle grass (Bot.), a marine plant (Thalassia
      testudinum) with grasslike leaves, common about the West
      Indies.

   Turtle shell, tortoise shell. See under Tortoise.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Alligator \Al"li*ga`tor\, n. [Sp. el lagarto the lizard (el
   lagarto de Indias, the cayman or American crocodile), fr. L.
   lacertus, lacerta, lizard. See Lizard.]
   1. (Zool.) A large carnivorous reptile of the Crocodile
      family, peculiar to America. It has a shorter and broader
      snout than the crocodile, and the large teeth of the lower
      jaw shut into pits in the upper jaw, which has no marginal
      notches. Besides the common species of the southern United
      States, there are allied species in South America.
      [1913 Webster]

   2. (Mech.) Any machine with strong jaws, one of which opens
      like the movable jaw of an alligator; as,
      (a) (Metal Working) a form of squeezer for the puddle
          ball.;
      (b) (Mining) a rock breaker;
      (c) (Printing) a kind of job press, called also alligator
          press.
          [1913 Webster]

   Alligator apple (Bot.), the fruit of the Anona palustris,
      a West Indian tree. It is said to be narcotic in its
      properties. --Loudon.

   Alligator fish (Zool.), a marine fish of northwestern
      America (Podothecus acipenserinus).

   Alligator gar (Zool.), one of the gar pikes (Lepidosteus
      spatula) found in the southern rivers of the United
      States. The name is also applied to other species of gar
      pikes.

   Alligator pear (Bot.), a corruption of Avocado pear. See
      Avocado.

   Alligator snapper, Alligator tortoise, Alligator turtle
      (Zool.), a very large and voracious turtle (Macrochelys
      lacertina) inhabiting the rivers of the southern United
      States. It sometimes reaches the weight of two hundred
      pounds. Unlike the common snapping turtle, to which the
      name is sometimes erroneously applied, it has a scaly head
      and many small scales beneath the tail. This name is
      sometimes given to other turtles, as to species of
      Trionyx.

   Alligator wood, the timber of a tree of the West Indies
      (Guarea Swartzii).
      [1913 Webster]