Answer

If you mean Aathai Tap in Jainism, it means fasting for 8 consecutive days, usually with only boiled water taken according to the tradition followed. ( jainsquare.wordpress.com)

Explanation

In Jain fasting terms, Aathai refers to an eight-day austerity. It is considered a strong form of tapa, and in some Jain communities the completion of the fast is observed with devotion and celebration. ( jainsquare.wordpress.com)

Spiritual Understanding

Aathai tap is practiced for self-discipline, purification, and detachment. In Jain Dharma, such tapas help reduce attachment to the body and strengthen inner purity. ( jaina.org)

Takeaway

So, in simple words: Aathai Tap = 8-day Jain fast. If you meant a different word by “Chatri,” the Jain term most commonly used is Aathai. ( jainsquare.wordpress.com)