Tib., gTer-ston: Treasure Discoverer
Tibetan term for an individual who discovers, finds, recovers, or reveals one or more previously hidden terma (treasures); hidden for the sake of future generations and/or because certain teachings were judged too advanced for the then living.
Especially members of the Nyingmapa used this "hide and recover" method for the transmission of their teachings; a sensible technique when considering the various phases of persecution early Tantric Buddhism had to survive. However, terma, especially of the "Mind Treasure" class, have been and are being revealed up to the present day and by members of all schools, including the Bönpo tradition.
The exact number of terton throughout history is unknown, yet there exists a list [Thondup 1986. p.189] which names 275 individuals from the 11th to the 20th century. All these terton are classified - as are the terma - into the categories earth or mind, but also according to the type(s) of teachings contained in their discoveries. One thus finds expressions such as minor, major, and great terton.
Among the 108 great ones, again five have a special status and are called Terma King:
Although most known terton are men, there are some exceptions (Kunga Bum for example). This is especially interesting in light of the fact that the revelation of most terma, i.e. those of the "Mind Treasure" variety (Tib., dgongs-gTer), is dependent on having a suitable partner for the rituals of the fulfillment yoga stage; rituals designed to achieve the necessary state of mind known as bliss-emptiness. It is in this state of heightened awareness and lucidity, that the terton experiences his or her visions and is able to first receive and then translate the revelation in question. Women, so it seems, are more often compassionate and giving for the sake of a fellow man (sustaining his bliss and vision); and/or most men possibly lack the ability to aid and sustain a woman in her efforts.
Another prerequisite for being/becoming a terton is the ability to consciously remember one or more of one's past lives; i.e. earlier incarnations, especially those in which the terton in question was a direct student of Padmasambhava (for an example, see the incarnation line Pema Sal to Pema Ledrel Tsal to Longchenpa).