What is the definition or description of: vasodilator?

Vessel relaxer: A vasodilator is a chemical that works to cause active relaxation of the blood vessels. These medications are chosen most often to treat high blood pressure, but may also be prescribed for the treatment of congestive heart failure or damaged heart valves, after heart surgery, or for pulmonary hypertension.

Blood vessel relaxer: Blood vessels have the capability of increasing or decreasing their diameter. When a blood vessel dilates, it generally leads to lowered blood pressure. Drugs that cause this are termed vasodilators. These can act on arteries or veins. Some classes of vasodilators include nitrates, calcium channel blockers and alpha-adrenergic blockers.