To know the mean of Hindu one will have to deep in history.. Actually the culture of India or the origin of Indians are from the Sindhu Civilization and in Persian Sindhu is called Hindu. That's so why the sindhu (people of Sindhu Civilization) called Hindu. On the name of Hindu's the name of the country is Hindustan. It is not any community or any religion but the fact it is citizenship.
There is a very interesting fact behind this also. The British Colonial Government wanted to divide Hindustan in more then 500 parts and they also succeed at one period of time they divided India in more then 500 parts in which East Pakistan (now Bangladesh) and West Pakistan (now Pakistan).
Knowing the fact of Hindu its very important to change the name of Hindustan by that they can easily divide our nation. So that the whole government made an uninhabitable labor and played a very nice politics and changed the name of our nation from Hindustan to India or Bharat.
Now I think that all Indian understand the means of Hindu and can call themselves proudly that we are HINDU.