Definition of tacks:
(n) :
A small nail with a flat head.
(n) :
A thumbtack.
(n) :
(sewing) A loose seam used to temporarily fasten pieces of cloth.
(n) :
(nautical) The lower corner on the leading edge of a sail relative to the direction of the wind.
(n) :
(nautical) A course or heading that enables a sailing vessel to head upwind.
(n) :
(figurative) A direction or course of action, especially a new one; a method or approach to solving a problem.