A passing
woman is simply a woman who passes as a
man. This may take on a variety of reasons, including just
crossdressing, being a
drag king or
transsexual, or just a
butch lesbian who is doing it
temporarily to avoid problems with others or for some similar situation.
There are a number of passing women in history who have lived for substantial amounts of time in a male gender role. Often the ones documented had relationships as a "normal" male would - with women.
A couple examples:
Murray Hall was a prominent politician in Tammany Hall for over 25 years, and was even married twice - to women. It was only after his death that it was discovered that his body was that of a female.
Dr. James Barry was a surgeon and officer, eventually promoted to medical inspector, in the British army for 40 years. He was well known too for his skill and being able to make quick decisions under pressure. He had even fought a duel. It wasn't until his death in 1865 that his physical sex was uncovered.
Billy Tipton is a well known example. He was a saxophone and piano player, involved in leading a number of Jazz bands in the 1940's and 1950's. He married several times, eventually to a stripper, and they adopted serveral children. In 1989, he was struck by a hemorrhaging ulcer, and his youngest child called an ambulance. As the paramedics tried to revive him, they all discovered that he had a female body.
And yes, as someone has soft linked below, Brandon Teena is a very modern example of a passing woman, along with a demonstration of what can happen when someone is found out.
There have even been a number of Saints that were passing women, many who lived as monks. Some examples are St Anastasia, St Eugenia/St Eugnios, and St Thekla.
There has been some debate among gay/lesbian and transgendered historians over the nature of passing women. May of the gay/lesbian crowd has been claiming passing women as prime examples of strong, feminist women role models. However, the transgendered crowd has started arguing that it is inappropriate to classify them in that manner - As they worked, lived, and loved as men, they offer a better fit as transgendered.
As maayan mentioned in a /msg to me, there is also the possibility that some of the people who have done this may have been partially influenced by the need to live as men to accomplish certain goals, as women have almost always been restricted in their options. I would hazard a guess that this surely couldn't be the only reason, but could quite well push someone who would consider such a thing anyways into doing it. It might be more applicatable to the Saints, than others who have done such.