define orthostatic
Orthostatic hypotension: A temporary lowering of blood pressure, usually related to suddenly standing up. Healthy people may experience orthostatic hypotension if they rise quickly from a seated position, especially after a meal. Orthostatic hypotension occurs most commonly in older people. The change in position causes a temporary reduction in blood flow and therefore a shortage of oxygen to the brain. This leads to lightheadedness, dizziness, and, sometimes, a temporary loss of consciousness.