s who can use multiple different forms of magic
- indeed, any possiple kind of magic - can be called bihexual.
In Raymond E. Feist's Midkemia books, there were two "paths" of magic, the Lesser Path and the Greater Path - Midkemians used Lesser Path, the Tsurani Great Ones used the Greater Path.
So, Pug was the first to be known as a bihexual magician, because he knew both "paths" with no problems (remember, there is no magic).
(OK, lame idea, but you got it - the society around has always been plagued by binary disease.)