NEXT TIME YOU'RE BORED you might take a few minutes and look up the names of weeds.  For plants considered to be such terrible things, they have wonderful names.
          Prostrate knotweed
          Common burdock
          Curly dock
          Purple deadnettle
          Toothed spurge... to name a few
My dictionary defines "weed" as a wild plant growing where it is not wanted and in competition with cultivated plants.  Weeds are uninvited guests.  But weeds can be beautiful things, with colorful flowers.  Some weeds -- the dandelion, for example -- are edible, both the leaves (young leaves are best) as well as the flowers (more beta-carotene than carrots).
According to the Bureau of Land Management, weeds can be native or non-native, invasive or non-invasive, and noxious or not noxious.  Legally, a noxious weed is any plant designated by Federal, state, or county government as injurious to public health, agriculture, recreation, wild life or property.  Purple loosestrife, a gorgeous flowering plant, is considered noxious because it somehow damages wetlands.  A noxious weed is also commonly defined as a plant that grows out of place and is "competitive, persistent, and pernicious."
Sort of like A-Rod of the NY Yankees...