|a. the pressure that opposes the motion of a piston on its exhaust stroke in an internal-combustion engine|
|b. the exhaust pressure in external combustion engines|
|2.||med the local pressure that builds up when fluid flow is obstructed in the cardiovascular or urinary systems|
back pressure n.
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.