Source : Webster's Revised Unabridged Dictionary (1913)

   3. (Naut.)
      (a) A rope used to hold in place the foremost lower
          corners of the courses when the vessel is closehauled
          (see Illust. of {Ship}); also, a rope employed to pull
          the lower corner of a studding sail to the boom.
      (b) The part of a sail to which the tack is usually
          fastened; the foremost lower corner of fore-and-aft
          sails, as of schooners (see Illust. of {Sail}).
      (c) The direction of a vessel in regard to the trim of her
          sails; as, the starboard tack, or port tack; -- the
          former when she is closehauled with the wind on her
          starboard side; hence, the run of a vessel on one
          tack; also, a change of direction.

   4. (Scots Law) A contract by which the use of a thing is set,
      or let, for hire; a lease. --Burrill.

   5. Confidence; reliance. [Prov. Eng.] --Halliwell.

   {Tack of a flag} (Naut.), a line spliced into the eye at the
      foot of the hoist for securing the flag to the halyards.
      

   {Tack pins} (Naut.), belaying pins; -- also called {jack
      pins}.

   {To haul the tacks aboard} (Naut.), to set the courses.

   {To hold tack}, to last or hold out. --Milton.