vasotonic /ˌveɪzoʊˈtɑnɪk/adjective 1noun 1forms 3 adjective1 •Affecting the tone of vessels (almost always with reference to blood vessels); that is, affecting the muscle tone of the smooth muscle in the walls of blood vessels, thus influencing blood flow within the lumen. noun1 •A substance (especially a drug) that is vasotonic, usually with reference to a drug that modifies the tone of vessel walls, such as a vasopressor or a phlebotonic. formsvasotonics · more vasotonic · most vasotonic