- a resistant pressure exerted by liquid or gas against the forward motion or flow of an exhaust or pipe system: Careful control of backpressure ensures an even supply of oil from the well.
- the pressure that opposes the motion of a piston on its exhaust stroke in an internal-combustion engine
- the exhaust pressure in external combustion engines
- med the local pressure that builds up when fluid flow is obstructed in the cardiovascular or urinary systems
- Pressure exerted upstream in the circulation as a result of obstruction to forward flow, as when congestion in the pulmonary circulation results from failure of the left ventricle.