[1] : The Collaborative International Dictionary of English v.0.48

knapweed \knap"weed`\, n. bot.
   the black centaury centaurea nigra; -- so called from the
   knoblike heads of flowers. called also bullweed.
   1913 webster
see also:
centaurea nigra bullweed 

[2] : WordNet (r) 2.0

knapweed
     n : any of various plants of the genus centaurea having purple
         thistlelike flowers

Knapweed >> K Words
Knapweed, definition of term: Knapweed
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