The Collaborative International Dictionary of English v.0.48:

Weed \Weed\, n. [OE. weed, weod, AS. we['o]d, wi['o]d, akin to
   OS. wiod, LG. woden the stalks and leaves of vegetables D.
   wieden to weed, OS. wiod[=o]n.]
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   1. Underbrush; low shrubs. [Obs. or Archaic]
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            One rushing forth out of the thickest weed.
                                                  --Spenser.
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            A wild and wanton pard . . .
            Crouched fawning in the weed.         --Tennyson.
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   2. Any plant growing in cultivated ground to the injury of
      the crop or desired vegetation, or to the disfigurement of
      the place; an unsightly, useless, or injurious plant.
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            Too much manuring filled that field with weeds.
                                                  --Denham.
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   Note: The word has no definite application to any particular
         plant, or species of plants. Whatever plants grow among
         corn or grass, in hedges, or elsewhere, and are useless
         to man, injurious to crops, or unsightly or out of
         place, are denominated weeds.
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   3. Fig.: Something unprofitable or troublesome; anything
      useless.
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   4. (Stock Breeding) An animal unfit to breed from.
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   5. Tobacco, or a cigar. [Slang]
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   Weed hook, a hook used for cutting away or extirpating
      weeds. --Tusser.
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