"greenweed" in the noun sense
1. woodwaxen, dyer's greenweed, dyer's-broom, dyeweed, greenweed, whin, woadwaxen, Genista tinctoria
small Eurasian shrub having clusters of yellow flowers that yield a dye common as a weed in Britain and the United States sometimes grown as an ornamental
Source: WordNet® (An amazing lexical database of English)
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