Tack1  —n. 1 small sharp broad-headed nail. 2 us drawing-pin. 3 long stitch for joining fabrics etc. Lightly or temporarily together. 4 (in sailing) direction, or temporary change of direction, esp. Taking advantage of a side wind (starboard tack). 5 course of action or policy (change tack). 6 sticky condition of varnish etc. —v. 1 (often foll. By down etc.) Fasten with tacks. 2 stitch lightly together. 3 (foll. By to, on, on to) add or append. 4  a change a ship's course by turning its head to the wind. B make a series of such tacks. [probably related to french tache clasp, nail]