knapweed noun. ['napwi:d] Orig. knopweed. LME.
[from KNOP noun + WEED noun¹. For the change of vowel cf. strop, strap.]
Any of several plants of the genus Centaurea, of the composite family, related to the thistles, with heads of usu. purple flowers and hard globular involucres; esp. (more fully lesser knapweed) hardhead, C. nigra, and (more fully greater knapweed) C. scabiosa, of chalk grassland.

[TahlilGaran] English Dictionary ▲