The crossword solution for the term 'Northeastern State of India' is Assam, which is a state located in the northeastern region of India. It is bordered by Bhutan, Arunachal Pradesh, Nagaland, Manipur, Mizoram, and Meghalaya. Assam is known for its rich culture and diverse wildlife, including the one-horned rhinoceros. It is also home to the Brahmaputra River, which is one of the largest rivers in India.