1. Union, 2. Spiritually, it means union with God
In Sanskrut, the word Hindu is broken up as hin + du. 'Hin' means to remove and 'du' means darkness. In other words, anyone who makes efforts to remove the darkness of spiritual ignorance (that is, a seeker), is a Hindu.
1. Eternal, 2. That which is always new, full of Chaitanya (Divine consciousness), 3. That which never ages