Synonyms for White Thistle (same or very similar meaning)
WordNet sense 1 (any plant of the genus Argemone having large white or yellow flowers and prickly leaves and stems and pods; chiefly of tropical America):
argemone, prickly poppy, devil's fig
WordNet sense 2 (spiny shrub with silvery-scurfy foliage of alkaline plains of southwestern United States and Mexico):
quail bush, Atriplex lentiformis, quail brush
From the ODE community, based on WordNet
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