1. n. [Well Completions]

A type of valve that incorporates a sliding gate to block fluid flow. The design of the valve operating and sealing systems typically requires that gate valves should be operated either fully open or fully closed.

See: fluid flow

2. n. [Production]

A straight-through pattern valve whose closure element is a wedge or parallel-sided slab, situated between two fixed seating surfaces with means to move it in or out of the flow stream in a direction perpendicular to the pipeline axis.