The Collaborative International Dictionary of English v.0.48:

Wrack \Wrack\, n.
   A thin, flying cloud; a rack.
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The Collaborative International Dictionary of English v.0.48:

Wrack \Wrack\, v. t.
   To rack; to torment. [R.]
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The Collaborative International Dictionary of English v.0.48:

Wrack \Wrack\, n. [OE. wrak wreck. See Wreck.]
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   1. Wreck; ruin; destruction. [Obs.] --Chaucer. "A world
      devote to universal wrack." --Milton.
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   2. Any marine vegetation cast up on the shore, especially
      plants of the genera Fucus, Laminaria, and Zostera,
      which are most abundant on northern shores.
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   3. (Bot.) Coarse seaweed of any kind.
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   Wrack grass, or Grass wrack (Bot.), eelgrass.
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The Collaborative International Dictionary of English v.0.48:

Wrack \Wrack\, v. t.
   To wreck. [Obs.] --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Wreck \Wreck\, n. [OE. wrak, AS. wr[ae]c exile, persecution,
   misery, from wrecan to drive out, punish; akin to D. wrak,
   adj., damaged, brittle, n., a wreck, wraken to reject, throw
   off, Icel. rek a thing drifted ashore, Sw. vrak refuse, a
   wreck, Dan. vrag. See Wreak, v. t., and cf. Wrack a
   marine plant.] [Written also wrack.]
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   1. The destruction or injury of a vessel by being cast on
      shore, or on rocks, or by being disabled or sunk by the
      force of winds or waves; shipwreck.
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            Hard and obstinate
            As is a rock amidst the raging floods,
            'Gainst which a ship, of succor desolate,
            Doth suffer wreck, both of herself and goods.
                                                  --Spenser.
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   2. Destruction or injury of anything, especially by violence;
      ruin; as, the wreck of a railroad train.
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            The wreck of matter and the crush of worlds.
                                                  --Addison.
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            Its intellectual life was thus able to go on amidst
            the wreck of its political life.      --J. R. Green.
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   3. The ruins of a ship stranded; a ship dashed against rocks
      or land, and broken, or otherwise rendered useless, by
      violence and fracture; as, they burned the wreck.
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   4. The remain of anything ruined or fatally injured.
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            To the fair haven of my native home,
            The wreck of what I was, fatigued I come. --Cowper.
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   5. (Law) Goods, etc., which, after a shipwreck, are cast upon
      the land by the sea. --Bouvier.
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WordNet (r) 3.0 (2006):

wrack
    n 1: dried seaweed especially that cast ashore
    2: the destruction or collapse of something; "wrack and ruin"
       [syn: wrack, rack]
    3: growth of marine vegetation especially of the large forms
       such as rockweeds and kelp [syn: sea wrack, wrack]
    v 1: smash or break forcefully; "The kid busted up the car"
         [syn: bust up, wreck, wrack]

Moby Thesaurus II by Grady Ward, 1.0:

138 Moby Thesaurus words for "wrack":
   algae, autophyte, bean, bloodbath, blue ruin, bracken, breakdown,
   breaking up, breakup, bring to ruin, brown algae, carnage,
   cataclysm, catastrophe, cave, cave-in, climber, collapse, condemn,
   conferva, confervoid, confound, consume, consumption, crack-up,
   crash, creeper, damn, damnation, deal destruction, debacle,
   decimate, decimation, demolish, depredate, depredation, desolate,
   desolation, despoil, despoilment, despoliation, destroy,
   destruction, devastate, devastation, devour, diatom, disaster,
   disintegration, disorganization, disruption, dissolution, dissolve,
   engorge, fern, fruits and vegetables, fucus, fungus, gobble,
   gobble up, grapevine, green algae, gulfweed, gut, gut with fire,
   havoc, hecatomb, herb, heterophyte, holocaust, incinerate, ivy,
   kelp, lay in ruins, lay waste, legume, lentil, liana, lichen,
   liverwort, mold, moss, mushroom, parasite, parasitic plant, pea,
   perdition, perthophyte, phytoplankton, planktonic algae,
   plant families, puffball, pulse, ravage, raze, red algae, rockweed,
   ruin, ruinate, ruination, rust, saprophyte, sargasso, sargassum,
   sea lentil, sea moss, sea wrack, seaweed, shambles, shipwreck,
   slaughter, smash, smashup, smut, spoliation, succulent, swallow up,
   throw into disorder, toadstool, total loss, unbuild, undo, undoing,
   unleash destruction, unleash the hurricane, unmake, upheave,
   vandalism, vandalize, vaporize, vetch, vine, washout, waste, wort,
   wrack and ruin, wreak havoc, wreck