Meaning

• To nail with a tack (small nail with a flat head).

• To sew/stich with a tack (loose seam used to temporarily fasten pieces of cloth).

• 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.

• To add something as an extra item.

  "to tack (something) onto (something)"

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

Meaning

• Loose temporary stitches in dressmaking etc.

• The act of changing tack.

• A union of securities given at different times, all of which must be redeemed before an intermediate purchaser can interpose a claim.

• The joining together of consecutive periods of possession of property, especially between squatters in cases of adverse possession.