what is the "true" definition of dissociation?

[qilora.livejournal.com]

and by "true" i mean (obviously) the: "modern medical definition" of the word...

every time i will sit and actually *think* on the word, and try to figure out what it is supposed to mean and how do we feel it (or not), i just end up looking at a bunch of blank faces in-house as the whole of us go "man, i have no friggin idea"....

for instance, how would doing things like "tuning out" background noise to concentrate on something you are trying to read, fit into the definition of dissociation?

thanks

- Jules.