• Webster's Revised Unabridged Dictionary
    • n Tanist In Ireland, a lord or proprietor of a tract of land or of a castle, elected by a family, under the system of tanistry. "This family [the O'Hanlons] were tanists of a large territory within the present county of Armagh."
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Century Dictionary and Cyclopedia
    • n tanist The chief, or holder of the lands and honors, in certain Celtic races; sometimes, the chief's chosen successor. See tanistry.
    • ***
Chambers's Twentieth Century Dictionary
    • n Tanist tan′ist the chief or holder of lands, &c., in certain Celtic races, also the chief's elective successor
    • ***


Webster's Revised Unabridged Dictionary
Ir. tanaiste, tanaise, second, the second person in rank, the presumptive or apparent heir to a prince
Chambers's Twentieth Century Dictionary
Ir. and Gael. tanaiste, lord—tan, country.


In literature:

You are all acquainted with the ways of the Tanist priests.
"The American Missionary, Vol. 43, No. 9, September, 1889" by Various
This story must have been an after-thought, to account for what we may suppose to have been a prehistoric Tanist stone.
"Roman Mosaics" by Hugh Macmillan
Thenceforward, however, we hear of the Archbishops, but not of the kings or tanists of Cashel.
"Insula Sanctorum et Doctorum" by John Healy