tum·ble·weed /ˈtʌmbəlˌwid/
 滾草
 Tum·ble·weed n. Bot. Any plant which habitually breaks away from its roots in the autumn, and is driven by the wind, as a light, rolling mass, over the fields and prairies; such as witch grass, wild indigo, Amarantus albus, etc.
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 tumbleweed
      n 1: any plant that breaks away from its roots in autumn and is
           driven by the wind as a light rolling mass
      2: prickly bushy Eurasian plant; a troublesome weed in central
         and western United States [syn: Russian thistle, Russian
         tumbleweed, Russian cactus, Salsola kali tenuifolia]
      3: bushy annual weed of central North America having greenish
         flowers and winged seeds [syn: winged pigweed, Cycloloma
         atriplicifolium]
      4: bushy plant of western United States [syn: Amaranthus albus,
          Amaranthus graecizans]