An inbetween between bisexual and straight. A person who is mainly straight but does sometimes find the same gender appealing. Most of them could imagine having a homosexual relationship, but they mainly have heterosexual relationships.
Vanessa: "Are you straight or bi?"
Ashley: "I'm about 90% straight and 10% bi, so I'm heteroflexible"
someone who is hetroflexible is straight but willing to get with/ experiment with someone of the same gender without being homosexual/bisexual
samantha is a hetroflexible girl because although she has had numerous boyfriends she is open to hooking up with/getting involved with another girl without being homosexual