What is theosis, and how does one attain it, according to EO theology?
This is the first I have heard the word but before I search into it deeper I will take a stab at its implication.
biggandyy sounds as if on the right tract with that comic answer. An osis is a condition like the bodies liver state from much alcohol or other contaminates.
Therefore I would say that it speaks of achieving the following:
2 Peter 1:4 "Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust."
I believe that the scriptures teach us that the main difference between lower animals and man is that man was created to bear the divine image. We are meant to bear it in a way that it completely envelops us throughout, like as an osis.
That is my best guess without researching it further.