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.The ‘Destroyer’ in the trinity of Hindu Deities, the other two are Brahmā and Shrīvishṇu, 2. Principle of Dissolution