the pressure exerted by the blood against the inner walls of the blood vessels, esp. the arteries, or the heart: it varies with health, age, emotional tension, etc.
See blood pressure in American Heritage Dictionary 4
noun Abbr. BP
The pressure exerted by the blood against the walls of the blood vessels, especially the arteries. It varies with the strength of the heartbeat, the elasticity of the arterial walls, the volume and viscosity of the blood, and a person's health, age, and physical condition.