He very well could have been, but he also was from Syria, and clearly heavily influenced by eastern culture. Elagabalus' style of dress and particularly wearing make up, would have been perceived as feminine to many romans, but in the east, such styles of dress were common amongst men. Transsexual may have been an attempt to explain Elagabalus' dress to the bewildered Romans, but it is more likely it was used as slander against him.