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]
H. P. Blavatsky and others sometimes referred to them indistinctly as "Brothers", "Adepts", or "Mahatmas." However, it seems the word "Master" refers more specifically to high 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]