Noun

1. A small nail with a flat head.
2. A loose seam used to temporarily fasten pieces of cloth.
3. (Wikipedia) The lower corner on the leading edge of a sail relative to the direction of the wind.
4. A course or direction that enables the vessel to head upwind. See also reach, gybe.
5. A direction or course of action, especially one that differs from the previous one.

   to try a different tack.

6. The maneuver by which a sailing vessel turns its bow through the wind so that the wind changes from one side to the other.
7. 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.
8. The stickiness of a compound, related to its cohesive and adhesive properties.

Verb

1. To secure with tacks.
2. To turn a vessel onto the other tack; come about.
3. To sail toward the direction of the wind by tacking repeatedly.

Verb

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 (Wikipedia).
4. To add something as an extra item.

   to tack (something) onto (something)

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

Noun

1. Lease, tenancy
2. The period of such a contract
3. A leasehold esp. the tenure of a land or a farm.

Etymology