noun a genus of biennial, poisonous, white-flowered, umbelliferous plants, bearing ribbed fruit ("seeds") and decompound leaves.
2. conium ·noun 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.