WordNet sense 1 (very spiny and dense evergreen shrub with fragrant golden-yellow flowers; common throughout western Europe):

furze, gorse, Irish gorse, Ulex europaeus

WordNet sense 2 (small Eurasian shrub having clusters of yellow flowers that yield a dye; common as weed in England and United States; sometimes grown as an ornamental):

dyer's-broom, dyeweed, greenweed, woadwaxen, woodwaxen, dyer's greenweed, Genista tinctoria

WordNet sense 3 (any of various hard colored rocks (especially rocks consisting of chert or basalt)):

whinstone