The Collaborative International Dictionary
dyer's broom
dyer's broom \dyer's broom\, dyer's-broom \dyer's-broom\n. small Eurasian shrub ( Genista tinctoria) having clusters of yellow flowers that yield a dye; common as weed in England and U.S.; sometimes grown as an ornamental.
Syn: woodwaxen, dyer's greenweed, dyer's weed, dyer's rocket, dyeweed, greenweed, whin, woadwaxen, Genista tinctoria.
Wiktionary
dyer's broom
n. A species of mignonette (''Reseda luteola''), used for dyeing yellow.