This question, like "What is the biological definition of life?" and "What images and sets count as 'fractals'?" is not as straightforward as it first appears!
In the end, glitch style is really determined by its look: patterns and textures that almost never occur naturally in apophysis. These patterns and textures can take many forms:
Keyhole by FarDareisMai
How are these patterns and textures achieved?
There is usually a strict deterministic xaos loop: Xform 1 feeds only to xform 2, which feeds only to xform 3, which feeds only back to xform 1. There is no branching, as in a more typical IFS. Sometimes, extremely unbalanced weights can give a similar effect.
Transforms often only a