The Collaborative International Dictionary of English v.0.48:

Ladder \Lad"der\ (l[a^]d"d[~e]r), n. [OE. laddre, AS.
   hl[=ae]der, hl[=ae]dder; akin to OFries. hladder, OHG.
   leitara, G. leiter, and from the root of E. lean, v.
   [root]40. See Lean, v. i., and cf. Climax.]
   1. A frame usually portable, of wood, metal, or rope, for
      ascent and descent, consisting of two side pieces to which
      are fastened cross strips or rounds forming steps.
      [1913 Webster]

            Some the engines play,
            And some, more bold, mount ladders to the fire.
                                                  --Dryden.
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   2. That which resembles a ladder in form or use; hence, that
      by means of which one attains to eminence; as, to climb
      the corporate ladder.
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            Lowliness is young ambition's ladder. --Shak.
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   Fish ladder. See under Fish.

   Ladder beetle (Zool.), an American leaf beetle (Chrysomela
      scalaris). The elytra are silvery white, striped and
      spotted with green; the under wings are rose-colored. It
      feeds upon the linden tree.

   Ladder handle, an iron rail at the side of a vertical fixed
      ladder, to grasp with the hand in climbing.

   Ladder shell (Zool.), a spiral marine shell of the genus
      Scalaria. See Scalaria.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fish \Fish\, n.; pl. Fishes (f[i^]sh"[e^]z), or collectively,
   Fish. [OE. fisch, fisc, fis, AS. fisc; akin to D. visch,
   OS. & OHG. fisk, G. fisch, Icel. fiskr, Sw. & Dan. fisk,
   Goth. fisks, L. piscis, Ir. iasg. Cf. Piscatorial. In some
   cases, such as fish joint, fish plate, this word has prob.
   been confused with fish, fr. F. fichea peg.]
   1. A name loosely applied in popular usage to many animals of
      diverse characteristics, living in the water.
      [1913 Webster]

   2. (Zool.) An oviparous, vertebrate animal usually having
      fins and a covering scales or plates. It breathes by means
      of gills, and lives almost entirely in the water. See
      Pisces.
      [1913 Webster]

   Note: The true fishes include the Teleostei (bony fishes),
         Ganoidei, Dipnoi, and Elasmobranchii or Selachians
         (sharks and skates). Formerly the leptocardia and
         Marsipobranciata were also included, but these are now
         generally regarded as two distinct classes, below the
         fishes.
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   3. pl. The twelfth sign of the zodiac; Pisces.
      [1913 Webster]

   4. The flesh of fish, used as food.
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   5. (Naut.)
      (a) A purchase used to fish the anchor.
      (b) A piece of timber, somewhat in the form of a fish,
          used to strengthen a mast or yard.
          [1913 Webster]

   Note: Fish is used adjectively or as part of a compound word;
         as, fish line, fish pole, fish spear, fish-bellied.
         [1913 Webster]

   Age of Fishes. See under Age, n., 8.

   Fish ball, fish (usually salted codfish) shared fine, mixed
      with mashed potato, and made into the form of a small,
      round cake. [U.S.]

   Fish bar. Same as Fish plate (below).

   Fish beam (Mech.), a beam one of whose sides (commonly the
      under one) swells out like the belly of a fish. --Francis.

   Fish crow (Zool.), a species of crow (Corvus ossifragus),
      found on the Atlantic coast of the United States. It feeds
      largely on fish.

   Fish culture, the artifical breeding and rearing of fish;
      pisciculture.

   Fish davit. See Davit.

   Fish day, a day on which fish is eaten; a fast day.

   Fish duck (Zool.), any species of merganser.

   Fish fall, the tackle depending from the fish davit, used
      in hauling up the anchor to the gunwale of a ship.

   Fish garth, a dam or weir in a river for keeping fish or
      taking them easily.

   Fish glue. See Isinglass.

   Fish joint, a joint formed by a plate or pair of plates
      fastened upon two meeting beams, plates, etc., at their
      junction; -- used largely in connecting the rails of
      railroads.

   Fish kettle, a long kettle for boiling fish whole.

   Fish ladder, a dam with a series of steps which fish can
      leap in order to ascend falls in a river.

   Fish line, or Fishing line, a line made of twisted hair,
      silk, etc., used in angling.

   Fish louse (Zool.), any crustacean parasitic on fishes,
      esp. the parasitic Copepoda, belonging to Caligus,
      Argulus, and other related genera. See Branchiura.

   Fish maw (Zool.), the stomach of a fish; also, the air
      bladder, or sound.

   Fish meal, fish desiccated and ground fine, for use in
      soups, etc.

   Fish oil, oil obtained from the bodies of fish and marine
      animals, as whales, seals, sharks, from cods' livers, etc.


   Fish owl (Zool.), a fish-eating owl of the Old World genera
      Scotopelia and Ketupa, esp. a large East Indian
      species (K. Ceylonensis).

   Fish plate, one of the plates of a fish joint.

   Fish pot, a wicker basket, sunk, with a float attached, for
      catching crabs, lobsters, etc.

   Fish pound, a net attached to stakes, for entrapping and
      catching fish; a weir. [Local, U.S.] --Bartlett.

   Fish slice, a broad knife for dividing fish at table; a
      fish trowel.

   Fish slide, an inclined box set in a stream at a small
      fall, or ripple, to catch fish descending the current.
      --Knight.

   Fish sound, the air bladder of certain fishes, esp. those
      that are dried and used as food, or in the arts, as for
      the preparation of isinglass.

   Fish story, a story which taxes credulity; an extravagant
      or incredible narration. [Colloq. U.S.] --Bartlett.

   Fish strainer.
      (a) A metal colander, with handles, for taking fish from a
          boiler.
      (b) A perforated earthenware slab at the bottom of a dish,
          to drain the water from a boiled fish.

   Fish trowel, a fish slice.

   Fish weir or Fish wear, a weir set in a stream, for
      catching fish.

   Neither fish nor flesh, Neither fish nor fowl (Fig.),
      neither one thing nor the other.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fish ladder
    n 1: a series of ascending pools providing a passage for salmon
         to swim upstream past a dam