Source : Webster's Revised Unabridged Dictionary (1913)

Tenace \Ten"ace\, n. [F. tenace tenacious, demeurer tenace to
   hold the best and third best cards and take both tricks, and
   adversary having to lead. See {Tenacious}.] (Whist)
   The holding by the fourth hand of the best and third best
   cards of a suit led; also, sometimes, the combination of best
   with third best card of a suit in any hand.