A sphygmomanometer is a medical device used to measure blood pressure. It typically consists of an inflatable cuff that wraps around the arm, a measuring unit (either a dial gauge or digital display), and a means to inflate the cuff, usually a bulb or automatic pump. When inflated, the cuff restricts blood flow, and as the pressure is gradually released, the device measures the systolic and diastolic pressures at which blood flow is detected. It's an essential tool for monitoring cardiovascular health.