monkshood

noun

1. (countable)Any of various poisonous plants, of the genus Aconitum, with blue or white flowers in the shape of a hood.

   “In the shady retreat under the hill grew clusters of luxuriant ferns; the wild French willow stood proudly with its lofty crest of red and gorgeous flowers between the pebbles, but the sedate monk's hood lifted its head still higher and looked gloomily and wickedly down on it, while it nodded and kept time to the cuckoo's song, as if it were counting how many days it had to live.”

2. (uncountable)The dried leaves or flowers of these plants formerly used as a source of medicinal alkaloids.