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1. A perennial North American herb (Oxypolis rigidior) in the parsley family, having pinnately compound leaves and umbels of small white flowers.
2. Any of several related plants, such as the water hemlock.
1. (Plants) Also called: water hemlock any of several N temperate poisonous umbelliferous marsh plants of the genus Cicuta, esp C. virosa, having clusters of small white flowers
2. (Plants) a similar and related plant, Oxypolis rigidior of the southeastern and central US
3. (Plants) any umbelliferous plant reputed to be poisonous to cattle
any of several poisonous plants of the parsley family, as Oxypolis rigidior, of swampy areas of North America, or the water hemlock, Cicuta maculata.