High Quality Content by WIKIPEDIA articles! A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to describe any plants that grow and reproduce aggressively. Generally, a weed is a plant in an undesired place.