When a person of a bisexual (or similarly ambiguous) orientation swings to a new preference towards men or women (especially if they had that preference previously).
Can develop as a defense mechanism to distract oneself from negative feelings from a present/past romantic interest.
"I'm unsatisfied with the way things are going with John. You know, instead of wallowing in my own despair and frustration, I think I'll play some Tegan and Sara and put myself in the swing-back. That's a great idea!"