ambiscuous
Being sexually ambiguous and promiscuous, characterized by switching from gender to gender very quickly. Different from bi-sexual because the ambisucous person will publicly assert that they are first gay, then straight, then gay, and so on.
Person 1 : Katherine hooked up with five girls last night!
Person 2: But she hooked up with that guy on Monday...
Person 1 : Katherine's ambiscuous, remember?