Tra từ hardheads - Từ điển WordNet v3.1

Từ điển WordNet v3.1 - WordNet Dictionary

hardheads

noun

a weedy perennial with tough wiry stems and purple flowers;
native to Europe but widely naturalized
• Syn:
lesser knapweed, black knapweed, Centaurea nigra
• Hypernyms:
knapweed