1. ( initial capital letter ) a Christian festival, observed on January 6, commemorating the manifestation of Christ to the gentiles in the persons of the Magi; Twelfth-day.
2. an appearance or manifestation, especially of a deity.
3. a sudden, intuitive perception of or insight into the reality or essential meaning of something, usually initiated by some simple, homely, or commonplace occurrence or experience.
4. a literary work or section of a work presenting, usually symbolically, such a moment of revelation and insight.
Pasted from <http://dictionary.reference.com/browse/Epiphany?r=66>
I use this word casually all the time in conversation–“I was reading this book on marriage and had an epiohany.” I use it in my writing too, especially when a character makes a life-altering realization. But I read it recently in its capital-letter form in a historical romance (Sins of the Highlander by Cannie Mason with Mia Marlowe) referring to the 12th day after Christmas and was reminded that it has other meanings, especially relating to religious culture.
I think it would also make a pretty name for a character. I might just have to use it sometime when it seems to fit a story.