1. (n.) A genus of biennial, poisonous, white-flowered, umbelliferous plants, bearing ribbed fruit (seeds) and decompound leaves.

2. (n.) The common hemlock (Conium maculatum, poison hemlock, spotted hemlock, poison parsley), a roadside weed of Europe, Asia, and America, cultivated in the United States for medicinal purpose. It is an active poison. The leaves and fruit are used in medicine.