The Sanskrit word Mahasiddha means a great Siddha or perfected being. It is a title given to one perceived to have attained virtually all spiritual perfections. Historically the Mahasiddha is an extreme rarity. Tibetan lists name eighty-four, among them the Nath saints Gorakshanath and Matsyendranath.
Within the International Nath Order this is not a grade and not an office. Adept is the English word for Siddha. Mahasiddha is the greater title of the old lists. Initiation does not confer it. The persons belong on their own pages. This page names the title.