In English it is written ad madan. I had no idea what it is in Hindi. The a's could be long or short. the d could be soft or hard D. So, we have 8 possiblities
Thanks to Har Mandir Singh 'Hamraaz', we have a page from the booklet of Indrasabha (1932) made by them.
Turns out it is "maadan". Remember that and spread the word :)
Now You Know!