Noxious weeds are plants that are considered to be harmful to the environment, agriculture, or human health. The term 'noxious weed' can refer to a variety of plants, including NETTLE (6 letters), LOCO (4 letters), and TARE (4 letters). NETTLE is an herbaceous plant with stinging hairs on its leaves and stems, which can cause skin irritation. LOCO is a poisonous plant found in western North America, which can cause neurological problems in livestock. TARE is a weed that is difficult to control and can reduce crop yields. All three of these plants are considered noxious weeds and can have a negative impact on the environment and human health.