Tra từ black knapweed - Từ điển WordNet v3.1

Từ điển WordNet v3.1 - WordNet Dictionary

black knapweed

noun

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