Adaab means honour or respect.
Adaab comes from the arabic word meaning respect and politeness.
Colloquially Adaab means Hello
It is a greeting accompanied with a hand gesture It is associated with the urdu-speaking communities of Uttar Pradesh, Hyderabad and Muhajir people of Pakistan.
Since the normal greeting of Muslims i.e. “Assalamu Alaikum” was meant for Muslims only, and Muslims in India lived in a multi-faith and a multi-lingual society, this alternative form of greeting was coined.
The gesture involves raising the right hand towards the face with palm inwards such that it is in front of the eyes and the finger tips are almost touching the forehead, as the upper torso is bent forward. It is typical for the person to say “adaab arz hai“, or just “adaab“. It is often answered with the same or the word “Tasleem” is said as an answer or sometimes it is answered with a facial gesture of acceptance.
In popular culture today, the adaab is often associated with the courtly culture of the Muslim Nawabs
urduwallahs 
How interesting. In Swahili, which has a lot of Arabic, Persian and some European influence, we use the word ‘adabu’ for good manners. It’s great to see how related languages can be.
Abadan has never been coined as an alternate, nor is it Nawabi culture. It is very commonly practiced with all denominations irrespective of religious practices. It is full of respect and reverence full of sincerity.
Aadab not Abadan.