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1.
One who attends the all-women's school Mills College located in Oakland, California. The large lesbian populaton leads one who is straight, or does not narrowly define her sexuality to be stuck in the strange sexual-limbo... known as being a "millsbian"
Chick A: "Damn! She's hella fine!"
Chick B: "You've been at Mills too long. Millsbian."
by Millllz September 13, 2006
 
2.
A woman who dates / sleeps with / 'experiments' with other women while attending Mills College, but reverts to heterosexuality once entering the Real World.
See also lesbian until graduation.
Hey, I didn't know she was gay!
Nah, she's just a millsbian.
by Susan Mills April 24, 2007