Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun hardheads
1 sense of hardheads
Sense 1
lesser knapweed, black knapweed, hardheads, Centaurea nigra -- (a weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized)
=> knapweed -- (any of various plants of the genus Centaurea having purple thistlelike flowers)