What's actually happening
A Full Moon happens when the Moon stands opposite the Sun from Earth's point of view. The lunar face is fully illuminated. A Full Moon in Libra means the Moon is in Libra while the Sun is in Aries — the axis of the individual and the relational, the self and the other.
The geometry is one of maximum contrast between personal will and the demands of genuine partnership.
What the tradition makes of it
Full Moons are culmination points. What was seeded at the New Moon has enough light on it to be seen. Libra adds a quality of social and aesthetic clarity to the culmination: the terms of a relationship, the fairness of an arrangement, the gap between what was promised and what has been delivered — these become visible and difficult to ignore.
The Aries Sun asserts the individual. The Libra Moon asks what the other person has experienced. The tension between them illuminates where self-interest and genuine reciprocity are in or out of alignment.
How to actually use it
Assess the important relationships honestly: what has been given and received, what has been asked for and withheld, where fairness has been maintained and where it has been avoided. This is good weather for direct conversations about the actual terms of a partnership.
When in doubt
Ask what the other person in this relationship has been experiencing that you have not fully attended to — and whether you are willing to let that information change the arrangement.