1. n. [Well Completions]

A downhole valve assembly that is designed to hold pressure from above while allowing fluids to flow from below. Standing valves generally are run and retrieved on slickline with the valve assembly located in an appropriate nipple. Applications for standing valves include testing the tubing string, setting packers, or other applications in which it is desirable to maintain fluid in the tubing string.

See: packer

2. n. [Production Testing]

In a subsurface sucker-rod pump, a valve that permits flow up the tubing to fill the pump-barrel chamber while preventing downward flow.

See: pump barrel,  rod pump