Say I have a moon orbiting a planet. Due to tidal locking, if we model the moon as a sphere, there exists an axis which passes through the center of the moon which is always pointed toward the center of mass of the orbited planet. This axis uniquely defines an orthogonal plane passing through the center of the moon, which intersects with the surface of the moon to uniquely define a particular meridian of the moon. How could I concisely refer to this meridian? As far as I have read, meridians of celestial bodies are typically defined relative to arbitrary "prime meridians" defined by well-known sites on the body's surface. I don't know if there's a general term for what I am looking for.
This is important for a minor plot point in a story I'm writing, wherein a mining company on a moon finds that their automated mining bots are having a harder time removing material at sites along this meridian.