back·pres·sure 
(băkprĕsh′ər)
(băkprĕsh′ər)n.
Residual pressure opposing the free flow of a gas or liquid, as in a pipe or an exhaust system.
- irrepressibility
- irrepressible
- irrepressibleness
- irrepressibly
- irreproachability
- irreproachable
- irreproachableness
- irreproachably
- irresistibility
- irresistible
- irresistibleness
- irresistibly
- irresoluble
- irresolute
- irresolutely
- irresoluteness
- irresolution
- irresolvable
- irrespective of
- irrespirable
- irresponsibility
- irresponsible
- irresponsibleness
- irresponsibly
- irresponsive