1. A plant considered undesirable, unattractive, or troublesome, especially one growing where it is not wanted, as in a garden.
2. Rank growth of such plants.
A water plant, especially seaweed.
3. The leaves or stems of a plant as distinguished from the seeds: dill weed.
4. Something useless, detrimental, or worthless, especially an animal unfit for breeding.
A dandelion is a common weed