Definition - What does Mahasamadhi mean?
Mahasamadhi is the state a yogi enters when they consciously make the decision to leave their body. This is only possible once they have already achieved God realization, or nirvikalpa samadhi, in which the yogi recognizes and experiences their true oneness and unity with God. To enter nirvikalpa samadhi is also to experience non-duality, where the perception of a duality of subject and object no longer exists. A yogi who has attained this is said to already dwell in a permanently enlightened state, which gives them the potential to enter mahasamadhi.
Mahasamadhi is a different experience to the death that happens for unenlightened beings. To enter mahasamadhi is an event that occurs only once. In making the decision to release their mortal body, the yogi also extinguishes their karma, thus ceasing the cycle of death and rebirth.
Yogapedia explains Mahasamadhi
Mahasamadhi is seen as the ultimate goal of any spiritual seeker. This is because any state of enlightenment that occurs while the yogi is in the physical realm is still limited by their physical body. When they enter mahasamadhi, they transcend their body. Their individual bubble of existence ends, and they become dissolved and liberated into the unity of everything.
To prepare for mahasamadhi, the yogi must first practice and apply discipline in their spiritual endeavours until they reach nirvikalpa samadhi. They may then incrementally ready themselves through their practice of samadhi. It is possible that they die during their sadhana practice, or during a specific disciplined preparation for their death. This process is unique and individual to each yogi.
The term, mahasamadhi, may also refer to the shrine of a great yogi. Such shrines are generally placed close to the location where the yogi entered mahasamadhi.