Real Dictionary

tack
countable noun: A tack is a short nail with a broad, flat head, especially one that is used for fastening carpets to the floor.
verb: If a sailing boat is tacking or if the people in it tack it, it is sailing towards a particular point in a series of sideways movements rather than in a straight line.
verb: If you tack pieces of material together, you sew them together with big, loose stitches in order to hold them firmly or check that they fit, before sewing them properly.
verb: If you tack something to a surface, you pin it there with tacks or drawing pins.

tack in American English
a short nail or pin, with a narrow shaft that is not tapered and a relatively large, flat head

tack in American English 1
noun: a short, sharp-pointed nail, usually with a flat, broad head

tack in American English 2
noun: food; fare

tack in American English 3
noun: a lease, esp. on farmland

tack in British English 1
noun: a short sharp-pointed nail, usually with a flat and comparatively large head
verb: to secure by a tack or series of tacks

tack in British English 2
noun: food, esp when regarded as inferior or distasteful

tack in British English 3
noun: riding harness for horses, such as saddles, bridles, etc

tack in British English 4
noun: a lease