Is 'cisgender' a word?

 

Even the great Julius Caesar, when interrogated by the Senate, famously could not tell the difference between Cisalpine and Transalpine Gaul. 

As I recall, the opening line of his history book Gender Wars reads thus: “Omnia genera in tres partes divisa est. Genus masculinum, genus femininum, et genus quodcumque aliquis male se esse credit.”