'Fa jing' means spontaneous energy release or 'jing release'. It is concerned with kinetic energy emission.
It is the means whereby energy can be transmitted from one person to another. 
It is not structure or movement or energy. It is the way in which the energy is emitted.

Fa jing is a means, not an end.

The harder you seek it, the more you try. Trying involves effort, effort causes tension, tension blocks energy and there is no fa jing.