tack

1. A small nail with a flat head.
2. A thumbtack.
3. A loose seam used to temporarily fasten pieces of cloth.
4. The lower corner on the leading edge of a sail relative to the direction of the wind.
5. A course or heading that enables a sailing vessel to head upwind. See also reach, gybe.
6. A direction or course of action, especially a new one.
7. The maneuver by which a sailing vessel turns its bow through the wind so that the wind changes from one side to the other.
8. The distance a sailing vessel runs between these maneuvers when working to windward; a board.
9. A rope used to hold in place the foremost lower corners of the courses when the vessel is close-hauled; also, a rope employed to pull the lower corner of a studding sail to the boom.
10. Any of the various equipment and accessories worn by horses in the course of their use as domesticated animals. Saddles, stirrups, bridles, halters, reins, bits, harnesses, martingales, and breastplates are all forms of horse tack.
11. The stickiness of a compound, related to its cohesive and adhesive properties.

    The laminate adhesive has very aggressive tack and is hard to move once in place.

12. Food generally; fare, especially of the bread kind.
13. That which is attached; a supplement; an appendix.
14. A contract by which the use of a thing is set, or let, for hire; a lease.
15. Confidence; reliance.

1. To nail with a tack (small nail with a flat head).
2. To sew/stich with a tack (loose seam used to temporarily fasten pieces of cloth).
3. To maneuver a sailing vessel so that its bow turns through the wind, i.e. the wind changes from one side of the vessel to the other.
4. To add something as an extra item.

   to tack (something) onto (something)

5. Often paired with "up", to place the tack on a horse.

1. A stain; a tache.
2. A peculiar flavour or taint.

   a musty tack

noun

That which is tacky; something cheap and gaudy.