Definition - What does Mahadeva mean?
Mahadeva is a Sanskrit term meaning "greatest god," "most powerful god" or "most supreme god." It is also the name sometimes given to the Hindu god, Shiva.
Shiva is regarded by many as the first yogi, or the guru of yoga. It is said that he taught yoga to the ancient rishis for the good of all mankind.
Yogapedia explains Mahadeva
Mahadeva is also the name of a figure in Buddhism who allegedly caused one of the first schisms between scholars of the early Buddhist schools, although many contest this. It is said that he caused this schism in his role as the founder of the Mahasamghikas, one of the early Buddhist schools associated with the development of Mahayana Buddhism.
Finally, the name, Mahadeva, is associated with another historical figure who founded the Caitika sect more than 100 years after the Buddhist schism.