The Collaborative International Dictionary of English v.0.48:

Squirrel \Squir"rel\ (skw[~e]r"r[e^]l or skw[i^]r"-; 277), n.
   [OE. squirel, OF. esquirel, escurel, F. ['e]cureuil, LL.
   squirelus, squirolus, scuriolus, dim. of L. sciurus, Gr.
   si`oyros; skia` shade + o'yra` tail. Cf. Shine, v. i.]
   1. (Zool.) Any one of numerous species of small rodents
      belonging to the genus Sciurus and several allied genera
      of the family Sciuridae. Squirrels generally have a
      bushy tail, large erect ears, and strong hind legs. They
      are commonly arboreal in their habits, but many species
      live in burrows.
      [1913 Webster]

   Note: Among the common North American squirrels are the gray
         squirrel (Sciurus Carolinensis) and its black
         variety; the fox, or cat, squirrel (Sciurus cinereus,
         or Sciurus niger) which is a large species, and
         variable in color, the southern variety being
         frequently black, while the northern and western
         varieties are usually gray or rusty brown; the red
         squirrel (see Chickaree); the striped, or chipping,
         squirrel (see Chipmunk); and the California gray
         squirrel (Sciurus fossor). Several other species
         inhabit Mexico and Central America. The common European
         species (Sciurus vulgaris) has a long tuft of hair on
         each ear. The so-called Australian squirrels are
         marsupials. See Petaurist, and Phalanger.
         [1913 Webster]

   2. One of the small rollers of a carding machine which work
      with the large cylinder.
      [1913 Webster]

   Barking squirrel (Zool.), the prairie dog.

   Federation squirrel (Zool.), the striped gopher. See
      Gopher, 2.

   Flying squirrel (Zool.). See Flying squirrel, in the
      Vocabulary.

   Java squirrel. (Zool.). See Jelerang.

   Squirrel corn (Bot.), a North American herb (Dicentra
      Canadensis) bearing little yellow tubers.

   Squirrel cup (Bot.), the blossom of the Hepatica triloba,
      a low perennial herb with cup-shaped flowers varying from
      purplish blue to pink or even white. It is one of the
      earliest flowers of spring.

   Squirrel fish. (Zool.)
      (a) A sea bass (Serranus fascicularis) of the Southern
          United States.
      (b) The sailor's choice (Diplodus rhomboides).
      (c) The redmouth, or grunt.
      (d) A market fish of Bermuda (Holocentrum Ascensione).


   Squirrel grass (Bot.), a pestiferous grass (Hordeum
      murinum) related to barley. In California the stiffly
      awned spikelets work into the wool of sheep, and into the
      throat, flesh, and eyes of animals, sometimes even
      producing death.

   Squirrel hake (Zool.), a common American hake (Phycis
      tenuis); -- called also white hake.

   Squirrel hawk (Zool.), any rough-legged hawk; especially,
      the California species Archibuteo ferrugineus.

   Squirrel monkey. (Zool.)
      (a) Any one of several species of small, soft-haired South
          American monkeys of the genus Callithrix. They are
          noted for their graceful form and agility. See
          Teetee.
      (b) A marmoset.

   Squirrel petaurus (Zool.), a flying phalanger of Australia.
      See Phalanger, Petaurist, and Flying phalanger under
      Flying.

   Squirrel shrew (Zool.), any one of several species of East
      Indian and Asiatic insectivores of the genus Tupaia.
      They are allied to the shrews, but have a bushy tail, like
      that of a squirrel.

   Squirrel-tail grass (Bot.), a grass (Hordeum jubatum)
      found in salt marshes and along the Great Lakes, having a
      dense spike beset with long awns.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wall \Wall\, n. [AS. weall, from L. vallum a wall, vallus a
   stake, pale, palisade; akin to Gr. ? a nail. Cf. Interval.]
   [1913 Webster]
   1. A work or structure of stone, brick, or other materials,
      raised to some height, and intended for defense or
      security, solid and permanent inclosing fence, as around a
      field, a park, a town, etc., also, one of the upright
      inclosing parts of a building or a room.
      [1913 Webster]

            The plaster of the wall of the King's palace. --Dan.
                                                  v. 5.
      [1913 Webster]

   2. A defense; a rampart; a means of protection; in the
      plural, fortifications, in general; works for defense.
      [1913 Webster]

            The waters were a wall unto them on their right
            hand, and on their left.              --Ex. xiv. 22.
      [1913 Webster]

            In such a night,
            Troilus, methinks, mounted the Troyan walls. --Shak.
      [1913 Webster]

            To rush undaunted to defend the walls. --Dryden.
      [1913 Webster]

   3. An inclosing part of a receptacle or vessel; as, the walls
      of a steam-engine cylinder.
      [1913 Webster]

   4. (Mining)
      (a) The side of a level or drift.
      (b) The country rock bounding a vein laterally. --Raymond.
          [1913 Webster]

   Note: Wall is often used adjectively, and also in the
         formation of compounds, usually of obvious
         signification; as in wall paper, or wall-paper; wall
         fruit, or wall-fruit; wallflower, etc.
         [1913 Webster]

   Blank wall, Blind wall, etc. See under Blank, Blind,
      etc.

   To drive to the wall, to bring to extremities; to push to
      extremes; to get the advantage of, or mastery over.

   To go to the wall, to be hard pressed or driven; to be the
      weaker party; to be pushed to extremes.

   To take the wall. to take the inner side of a walk, that
      is, the side next the wall; hence, to take the precedence.
      "I will take the wall of any man or maid of Montague's."
      --Shak.

   Wall barley (Bot.), a kind of grass (Hordeum murinum)
      much resembling barley; squirrel grass. See under
      Squirrel.

   Wall box. (Mach.) See Wall frame, below.

   Wall creeper (Zool.), a small bright-colored bird
      (Tichodroma muraria) native of Asia and Southern Europe.
      It climbs about over old walls and cliffs in search of
      insects and spiders. Its body is ash-gray above, the wing
      coverts are carmine-red, the primary quills are mostly red
      at the base and black distally, some of them with white
      spots, and the tail is blackish. Called also spider
      catcher.

   Wall cress (Bot.), a name given to several low cruciferous
      herbs, especially to the mouse-ear cress. See under
      Mouse-ear.

   Wall frame (Mach.), a frame set in a wall to receive a
      pillow block or bearing for a shaft passing through the
      wall; -- called also wall box.

   Wall fruit, fruit borne by trees trained against a wall.

   Wall gecko (Zool.), any one of several species of Old World
      geckos which live in or about buildings and run over the
      vertical surfaces of walls, to which they cling by means
      of suckers on the feet.

   Wall lizard (Zool.), a common European lizard (Lacerta
      muralis) which frequents houses, and lives in the chinks
      and crevices of walls; -- called also wall newt.

   Wall louse, a wood louse.

   Wall moss (Bot.), any species of moss growing on walls.

   Wall newt (Zool.), the wall lizard. --Shak.

   Wall paper, paper for covering the walls of rooms; paper
      hangings.

   Wall pellitory (Bot.), a European plant (Parictaria
      officinalis) growing on old walls, and formerly esteemed
      medicinal.

   Wall pennywort (Bot.), a plant (Cotyledon Umbilicus)
      having rounded fleshy leaves. It is found on walls in
      Western Europe.

   Wall pepper (Bot.), a low mosslike plant (Sedum acre)
      with small fleshy leaves having a pungent taste and
      bearing yellow flowers. It is common on walls and rocks in
      Europe, and is sometimes seen in America.

   Wall pie (Bot.), a kind of fern; wall rue.

   Wall piece, a gun planted on a wall. --H. L. Scott.

   Wall plate (Arch.), a piece of timber placed horizontally
      upon a wall, and supporting posts, joists, and the like.
      See Illust. of Roof.

   Wall rock, granular limestone used in building walls. [U.
      S.] --Bartlett.

   Wall rue (Bot.), a species of small fern (Asplenium
      Ruta-muraria) growing on walls, rocks, and the like.

   Wall spring, a spring of water issuing from stratified
      rocks.

   Wall tent, a tent with upright cloth sides corresponding to
      the walls of a house.

   Wall wasp (Zool.), a common European solitary wasp
      (Odynerus parietus) which makes its nest in the crevices
      of walls.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Hordeum murinum
    n 1: European annual grass often found as a weed in waste ground
         especially along roadsides and hedgerows [syn: barley
         grass, wall barley, Hordeum murinum]