The female character has some compelling reason to live as a male, often to avoid physical danger while traveling, or to take advantage of greater adventure or job opportunities. This is a particularly common way for YA fiction to explore gender issues. "Passing women" have shown up in plenty of non-SF works as well, again, particularly in YA fiction. "Passing women" are part of a broader phenomena of, usually, members of discriminated-against classes "passing" themselves as members of the privileged classes. Passing is full-time and intended to pass, as opposed to cross-dressing, which may not be intended to "pass". Examples:
"Red Tornado" (Abigail Mathilda "Ma" Hunkel) was a golden age DC superhero who wore longjohn-style tights and a pot on her head. (She has since gone on to play a woman in her 80s who acts as a parental figure to the Justice Society of America members)
Carol Guess. Switch (1998) - magic realism novel, with a passing woman as one of the narrators and characters
Gwyneth Jones . Divine Endurance (1984) (the character Cho, a female, sometimes passes as a boy, although this is by no means a primary aspect of the plot)
Maureen McHugh . Mission Child (on another planet, a woman begins dressing as a man for safety during war, and then continues to explore her male side, ultimately identifying rather androgynously)
"Red Tornado" (Abigail Mathilda "Ma" Hunkel) was a golden age DC superhero who wore longjohn-style tights and a pot on her head. (She has since gone on to play a woman in her 80s who acts as a parental figure to the Justice Society of America members)
