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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