The phrase "common weed" refers to a plant that is found in many places and is considered undesirable because it grows easily and can harm other plants in a garden or field. Full definition
Among the most common weeds in chile are broadleaves including spurred anoda (Anoda cristata), Wright's groundcherry (Physalis wrightii), tall morninglory (Ipomoea purprea), and Palmer amaranth (Amaranthus palmeri). (southwestfarmpress.com)
One of the most common weed killers used on suburban lawns in the United States depresses reproduction in lab mice. (sciencemag.org)
The atrazine (AT - truh - zeen) she mentioned is one of the most common weed killers used in the United States. (sciencenewsforstudents.org)