Masters of Wisdom
The Masters of Wisdom, or simply "The Masters" were defined by H. P. Blavatsky in the glossary of her book The Key To Theosophy as follows:
Master. A translation from the Sanskrit Guru, "Spiritual teacher," and adopted by the Theosophists to designate the Adepts, from whom they hold their teachings.[1]
The Masters of Wisdom are sometimes referred indistinctly as "Brothers", "Adepts", or "Mahatmas." However, it seems the word "Master" refers more specifically to a high class of Adepts who work in line with the evolutionary movement. This idea is reported by Charles Johnston in his interview to Mme. Blavatsky:
Then she told me something about other Masters and adepts she had known--for she made a difference, as though the adepts were the captains of the occult world, and the Masters were the generals.[2]