Source : Webster's Revised Unabridged Dictionary (1913)

Tortoise \Tor"toise\, n. [OE. tortuce, fr. OF. tortis crooked,
   fr. L. tortus isted, crooked, contorted, p. p. of torquere,
   tortum, to wind; cf. F. tortue tortoise, LL. tortuca,
   tartuca, Pr. tortesa crookedness, tortis crooked. so called
   in allusion to its crooked feet. See {Torture}.]
   1. (Zo["o]l.) Any one of numerous species of reptiles of the
      order Testudinata.

   Note: The term is applied especially to the land and
         fresh-water species, while the marine species are
         generally called turtles, but the terms tortoise and
         turtle are used synonymously by many writers. see
         {Testudinata}, {Terrapin}, and {Turtle}.

   2. (Rom. Antiq.) Same as {Testudo}, 2.

   {Box tortoise}, {Land tortoise}, etc. See under {Box},
      {Land}, etc.

   {Painted tortoise}. (Zo["o]l.) See {Painted turtle}, under
      {Painted}.

   {Soft-shell tortoise}. (Zo["o]l.) See {Trionyx}.

   {Spotted tortoise}. (Zo["o]l.) A small American fresh-water
      tortoise ({Chelopus, or Nanemys, quttatus}) having a
      blackish carapace on which are scattered round yellow
      spots.

   {Tortoise beetle} (Zo["o]l.), any one of numerous species of
      small tortoise-shaped beetles. Many of them have a
      brilliant metallic luster. the larv[ae] feed upon the
      leaves of various plants, and protect themselves beneath a
      mass of dried excrement held over the back by means of the
      caudal spines. The golden tortoise beetle ({Cassida
      aurichalcea}) is found on the morning-glory vine and
      allied plants.

   {Tortoise plant}. (Bot.) See {Elephant's foot}, under
      {Elephant}.

   {Tortoise shell}, the substance of the shell or horny plates
      of several species of sea turtles, especially of the
      hawkbill turtle. It is used in inlaying and in the
      manufacture of various ornamental articles.

   {Tortoise-shell butterfly} (Zo["o]l.), any one of several
      species of handsomely colored butterflies of the genus
      {Aglais}, as {A. Milberti}, and {A. urtic[ae]}, both of
      which, in the larva state, feed upon nettles.

   {Tortoise-shell turtle} (Zo["o]l.), the hawkbill turtle. See
      {Hawkbill}.

Source : WordNet®

tortoise
     n : usually herbivorous land turtles having clawed elephant-like
         limbs; worldwide in arid area except Australia and
         Antarctica