knotweed
nounAny of various low-growing or shrubby plants of the family Polyganaceae, having jointed stems and small flowers.
nounA plant of one of the species of knapweed or knobweed, Centaurea nigra, C. Cyanus, and C. Scabiosa: so called from the knot-like heads.
nounA plant of the genus Polygonum, which includes the doorweed, the smartweeds and water-pepper, the prince’s-feather, etc.; knotgrass or jointweed: so called from the knotty stem.
nounSee
Any of several