Source : Webster's Revised Unabridged Dictionary (1913)

Pressor \Press"or\, a. (Physiol.)
   Causing, or giving rise to, pressure or to an increase of
   pressure; as, pressor nerve fibers, stimulation of which
   excites the vasomotor center, thus causing a stronger
   contraction of the arteries and consequently an increase of
   the arterial blood pressure; -- opposed to {depressor}.
   --Landois & Stirling.

Source : WordNet®

pressor
     adj : increasing (or tending to increase) blood pressure; "pressor
           reflexes"