"God became man that we may become God."
Theosis - divinization - deification: said to be synonyms; only the last is in my Webster's.
I was all set to write a revelatory post on this subject when I found that someone else had already done a better job than I could ever do.
This is said to be Eastern Orthodox theology to a much great degree than it is in the West. Daniel Clendenin a convert from evangelicalism, has treated theosis exhaustively in his little book Eastern Orthodox Christianity (1994). As a convert Dan is very partial; nevertheless he provides much useful factual information. He cited a plethora of biblical and patristic quotes pointing to the deification of the believer. I found this one (of his own) quite striking: "The historical witness of Orthodoxy's sacramental life and theological literature both... repeatedly define salvation as divinization" (page 127).
Eastern Orthodoxy is not high on my list of favorite denominations, but I must express a pronounced preference of this definition of salvation over that of the tradionalists.
The doctrine of theosis puts the trinity in a new light. Many modern thinkers tell us that 3 is an incomplete number. Carl Jung, and some others have proposed adding Mary and making it a quaternity.
For Protestants theosis leads to the idea that the 4th member of the godhead might be humanity.