[hel.le.bore] n [ME elebre, fr. L elleborus, helleborus, fr. Gk helleboros] (15c) 1: any of a genus (Helleborus) of poisonous herbs of the buttercup family having showy flowers with petaloid sepals; also: the dried rhizome or an extract or powder of this formerly used in medicine
2: a poisonous herb (genus Veratrum) of the lily family; also: the dried rhizome of a hellebore (Veratrum album or V. viride) or a powder or extract of this containing alkaloids used as a cardiac and respiratory depressant and as an insecticide