Veg*n is a way to refer to "vegan or vegetarian", the asterisk acting as a wildcard replacing whatever letters seem most appropriate. This is a fairly useless convention, as all vegans are vegetarians, and therefore referring to 'vegetarians' would indicate the same set as veg*n and be pronounceable.
It is sometimes useful when you need a plural for vegetarians and want to indicate that at least some of your set are (or at least, may be) vegans and some are vegetarians, e.g., "meals for v*gans are available."
The term 'veg*an' is also used, as are the forms 'veg*nism' and 'veg*anism'.
Brevity Quest 2016