A psychic circle can mean a variety of things, but let's focus on one of the building blocks of psychic activity.
A psychic observes motion and change. A psychic circle is a motion that changes into the same thing - there is constant change, but from some viewpoints it looks like it's not changing at all.
Such motions, such psychic circles create form as we know it.
On a more general level, psychic energy flows that are consistent, stable and permanent can also be called a psychic circle. For example, a healthy human has a healthy psychic circle of energies.
The important thing to remember about psychic circles is that they can easily become psychic spirals: an advance upwards to a higher spiritual level or a downward spiral of being imprisoned by form.
A psychic, especially a psychic healer, has to be able to observe and balance psychic circles and the motions of psychic energy within and outside of our human selves.