Omnisexuals are attracted equally to all human beings (men, women, transexuals, etc.) They tend to go through phases of gender attraction that switch frequently and will eventually settle down with whoever wins their heart, regardless of said person's gender.
Basically, it's a broad term used to refer to any and all sexual orientations, expressions, and so forth. From homosexuals, to transgenders, to sometimes people with foot fetishes, someone who is omnisexual will love you for who you are.
(Based off my own definition of the term)
One of the doctors in Doctor Who *Confirmed*
Myself (Is an omnisexual)
not to be confused with the heralded Omnisexual: one who distributes his/her sexual affection in and around the Atlanta area esp. near the Omni arena and recently any other arena in the area