The Collaborative International Dictionary of English v.0.48:

overgrown \overgrown\ adj.
   1. covered with growing plants.
      [WordNet 1.5]

   2. abounded in usually unwanted vegetation. [Narrower terms:
      wooded (vs. unwooded); weedy]
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Weedy \Weed"y\, a. [Compar. Weedier; superl. Weediest.]
   [1913 Webster]
   1. Of or pertaining to weeds; consisting of weeds. "Weedy
      trophies." --Shak.
      [1913 Webster]

   2. Abounding with weeds; as, weedy grounds; a weedy garden;
      weedy corn.
      [1913 Webster]

            See from the weedy earth a rivulet break. --Bryant.
      [1913 Webster]

   3. Scraggy; ill-shaped; ungainly; -- said of colts or horses,
      and also of persons. [Colloq.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Weedy \Weed"y\, a.
   Dressed in weeds, or mourning garments. [R. or Colloq.]
   [1913 Webster]

         She was as weedy as in the early days of her mourning.
                                                  --Dickens.
   [1913 Webster]
   [1913 Webster]

WordNet (r) 3.0 (2006):

weedy
    adj 1: abounding with or resembling weeds; "a weedy path";
           "weedy plants that take over a garden" [ant: weedless]
    2: being very thin; "a child with skinny freckled legs"; "a long
       scrawny neck" [syn: scraggy, boney, scrawny, skinny,
       underweight, weedy]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "weedy":
   botanic, bulbous, cereal, dense, exuberant, farinaceous,
   flourishing, fruitlike, fruity, gross, heavy, herbaceous, herbal,
   herbose, herbous, herby, impenetrable, jungled, jungly, leguminose,
   leguminous, lush, luxuriant, overgrown, overrun, plantlike,
   radicated, radiciform, radicular, rank, rhizoid, riotous, rootlike,
   thick, tuberous, unweeded, vegetable, vegetal, vegetarian,
   vegetational, vegetative, weed-choked, weed-ridden