WordNet (r) 3.0 (2006):

Pitressin
    n 1: hormone secreted by the posterior pituitary gland (trade
         name Pitressin) and also by nerve endings in the
         hypothalamus; affects blood pressure by stimulating
         capillary muscles and reduces urine flow by affecting
         reabsorption of water by kidney tubules [syn:
         vasopressin, antidiuretic hormone, ADH, Pitressin]