No, it is not. It is a noun.
Holocaust in this term is used as an adjective describing the noun denial.A noun functioning as an adjective to describe another noun, called an attributive noun.
The Holocaust
To remember the Holocaust.
The Holocaust is a concept not a person.
The Holocaust wasn't a war. Please see the related questions.
One aspect of the Holocaust is murder, there was a lot of killing in the Holocaust.
The Holocaust started in Europe.
There were no elections in Germany in the Holocaust.
no, but enslavement was part of the Holocaust.
she was a girl in the holocaust
'The Holocaust'.
There was no 'Holocaust flag'. I wonder if you are confusing the Holocaust with something else?