Used in html and certain message board markup, the slash (/) means end (ex. for bold text, use b to start the bold text and /b to end it, note the slash), so /self means end self, aka kill yourself.

The field of psychology attempts to define it with circular definitions. The truth is, we don't really know how to define self... not objectively at least.
In a few words, self is consciousness. Consciousness escapes objective description (poor example: your experience of the colour red, is it the same as mine?). If a definition requires an objective description, then self is un-definable.

The act of selfsucking, autofellatio

To Will Self, i.e.

a)to be a complete legend, hilarious and know every word in the dictionary.

b)to speak in a terrifically deadpan, smokers drawl and appear on "Shooting Stars"

Selfed to be self-sufficient self-reliant. To make your own way.

ones own personality and being

When a homosexual male curves his cock downward over his taint into his ass.