Bipolar flow junction
A bipolar flow junction was a conduit branch within the plasma feeds of a starship warp propulsion system. It was attached directly to the secondary warp plasma feed. 

In 2374, Miles O'Brien believed he, Julian Bashir and Jadzia Dax had almost reached the bipolar flow junction of the . His uncertainty was due to the fact that they and the runabout they were travelling in, the , had shrunk down to a size small enough to fly through the Defiant, and he wasn't used to viewing the latter ship from that point of view. ()
Propulsion technology