||Co*ni"um (? or &?;), n. [NL., fr. Gr. &?; hemlock.] 1. (Bot.) A genus of biennial, poisonous, white-flowered, umbelliferous plants, bearing ribbed fruit ("seeds") and decompound leaves.

2. (Med.) 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.