Hypertension is defined as abnormally high blood pressure, the force at which blood is pumped into the heart when it comes from the arteries.
An example of hypertension is a heart that has to work extra hard to properly circulate blood through the body, increasing the size of the heart muscle and causing the heart chambers to get bigger, and either too weak or too stiff to pump blood properly.
See hypertension in Webster's New World College Dictionary
See hypertension in American Heritage Dictionary 4
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