According to UrbanDictionary, the word Heteroflexible refers to: "A person who identifies themselves as primarily heterosexual but can find the same sex sexually appealing."
About's guide to lesbian life offers an alternative definition: "A heteroflexible is a person who is straight but has a queer sensibility. They usually have lots of gay friends, identify with gay and lesbian culture and work for gay and lesbian rights."
Though I have mixed feelings about Katy Perry's song, I Kissed a Girl, interview that would seem to use both definitions.
Perry explained that though she kissed a girl, "I'm not a lesbian. I encourage anybody to try anything, just make sure you have integrity and character. It doesn't matter who anyone loves. I am for gay rights and I also have a boyfriend."
Given the fact that Perry probably isn't the only one who has had this type of experience and who feels like this, maybe it is useful to have a catchall term.
As Jamie, a GLBT Teens reader explained:
I’m sixteen and heteroflexible? Or maybe not. I’ve never really identified with the term bisexual, but I’m attracted to both sexes and have had a girlfriend for a blissful period of months, and would LOVE to find a girl to be with now, so what does that make me? People say regardless of what I want to be called, liking boys and girls makes me bi, but if there’s such a thing as heterosexual [that's how I'd identify.]
Of course, there is some debate over this term. Some people think the term heteroflexible is a legitimate way to describe oneself. Others worry that people who might otherwise identify as bisexual would rather say they're heteroflexible because it is less loaded.
There is no one consensus, so for now it is probably best, to just go with the term that you are most comfortable with!