"Womyn" is one of a number of alternative spellings of the word "women" used by some radical feminist writers. There are many alternative spellings, including "wimmin", "womban", "wom!n", "wom@n", "wohgmon". Writers who use alternative spellings see them as an expression of female independence and a repudiation of traditions that define females by reference to a male norm.
Read more about Womyn: Background