Opposition
Two points 180° apart, facing each other across the ecliptic.
An opposition is an axis: the two ends pull against each other and also define each other. Often described as external conflict, though more often it shows up as two things you want, placed at opposite ends.
A full moon is a Sun–Moon opposition, which is why full moons carry that quality of being pulled two ways and having to see clearly. That's geometry, not metaphor.