a genus of perennial herbs (helleborus) of the crowfoot family, mostly having powerfully cathartic and even poisonous qualities. h. niger is the european black hellebore, or christmas rose, blossoming in winter or earliest spring. h. officinalis was the officinal hellebore of the ancients.-any plant of several species of the poisonous liliaceous genus veratrum, especially v. album and v. viride, both called white hellebore.