any of several rhododendrons, as the great laurel of eastern North America or Rhododendron macrophyllum, of the west coast of North America.
British. the willow herb, Epilobium angustifolium.
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British Dictionary definitions for rosebay
US any of several rhododendrons, esp Rhododendron maximum of E North America
rosebay willowherb a perennial onagraceous plant, Chamerion (formerly Epilobium) angustifolium, that has spikes of deep pink flowers and is widespread in open places throughout N temperate regions
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