what is meant by the term …

The word 'secular' was put in the preamble to the constitution through the 42nd Amendment simply to reaffirm the faith of the nation in making the national politics stay above petty religious considerations while showing duerespect to all religions. The term, 'secular' means that the state has no religion of its own. The stateis neither religious nor anti-religions. The state observes complete neutrality in religious matters. India is a secular state. In Indian Constitution from article 25 to 28, the Right to Freedom of Religion has been granted to all the persons residing in India.
The 45th Amendment lays down that the term'secular' means that all religions carry equal respect and recognition from the state.
No doubt that India is a secular state. No discrimination is ever made against any individual because of his/her religion. All the people in India, forming different groups, sects, communities, etc. Everybody is equal before law, and enjoys equal rights.