Definitions of tack:

• noun:   sailing a zigzag course
• noun:   (nautical) the act of changing tack
• noun:   a short nail with a sharp point and a large head
• noun:   the heading or position of a vessel relative to the trim of its sails
• noun:   (nautical) a line (rope or chain) that regulates the angle at which a sail is set in relation to the wind
• noun:   gear for a horse
• verb:   fasten with tacks

  Example: "Tack the notice on the board"

• verb:   turn into the wind

  Example: "The sailors decided to tack the boat"

• verb:   reverse (a direction, attitude, or course of action)
• verb:   sew together loosely, with large stitches
• verb:   fix to; attach
• verb:   make by putting pieces together

  Example: "He tacked together some verses"

• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #10970)