slang One who identifies as mostly, but not completely, heterosexual. Because "hetero" here indicates one's primary sexual orientation, the term is seen by some as a more specific alternative to "bisexual" and by others as a label that discounts or erases bisexuality. I usually think of myself as heteroflexible because, even though I'm a woman who's only dated men, I don't think I'm 100% straight either.