biheterosexual Share definition Flag one who claims that one is heterosexual but actually bisexual. Guy, don't believe him. He is a biheterosexual. Once I saw hem getting between the sheets with another man. biheterosexual by Uttam Maharjan 2 July 23, 2014 0 0 Get merch Get the biheterosexual mug. Buy Now — $32.95 See more merch