Source : Webster's Revised Unabridged Dictionary (1913)

Vasoconstrictor \Vas`o*con*strict"or\, a. (Physiol.)
   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}.