[knap.weed] n [ME knopwed, fr. knop knop + wed weed] (15c): any of various weedy centaureas; esp: a widely naturalized European perennial (Centaurea nigra) with tough wiry stems and knobby heads of purple flowers
KNAPWEED
Meaning of KNAPWEED in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012