Homoflexible is a sexuality and/or romantic orientation in which one is homosexual/homoromantic, but occasionally feels an attraction or is open to a relationship with the opposite gender.
Homoflexibility is different from being bisexual/biromantic; a bisexual/biromantic person always feels attraction to two genders (though they may have a preference), while a homoflexible person will only occasionally feel an attraction to the opposite gender or simply be open to a relationship.
Oftentimes, this is used when someone's partner transitions.
The opposite of homoflexible is heteroflexible.