First of all - The Nazis called it "Endlösung" (Final Solution), "Die Judenfrage" (the Question about the Jews) or other likewise Euphemism.

Holocaust was used for the killing of people since medieval times and genocide since the Armenian genocide.

I know the naming is complicated, but as far as I remeber, using the term holocaust for the killing of all the people, and not only Jews, is more correct. Because otherwise, other groups like the queer, the Sinti and the Roma are much likly forgotten.

In my opinion, its hard to find a suitable word for this abomination. Some speeches in Germany I heard refering to it, talked around the word or said things like the million timed killing of people and families, but even this leaves alot out of this atrocity. And by my effort to make a short reference to a complex topic, I use holocaust. But if you have something better, please tell me.