Webster's Revised Unabridged Dictionary · 1913

(Physiology) Causing constriction of the blood vessels; as, the vasoconstrictor nerves, stimulation of which causes constriction of the blood vessels to which they go. These nerves are also called vasohypertonic.

(Medicine, Physiology) A substance which causes constriction of the blood vessels. Such substances are used in medicine to raise abnormally low blood pressure.