a short, sharp-pointed nail, usually with a flat, broad head.

Nautical .

a rope for extending the lower forward corner of a course.

the lower forward corner of a course or fore-and-aft sail.

the heading of a sailing vessel, when sailing close-hauled, with reference to the wind direction.

a course run obliquely against the wind.

one of the series of straight runs that make up the zigzag course of a ship proceeding to windward.

a course of action or conduct, esp. one differing from some preceding or other course.

one of the movements of a zigzag course on land.

a stitch, esp. a long stitch used in fastening seams, preparatory to a more thorough sewing.

a fastening, esp. of a temporary kind.

stickiness, as of nearly dry paint or glue or of a printing ink or gummed tape; adhesiveness.

the gear used in equipping a horse, including saddle, bridle, martingale, etc.

to fasten by a tack or tacks

to tack a rug to the floor.

to secure by some slight or temporary fastening.

to join together; unite; combine.

to attach as something supplementary; append; annex (often fol. by on or onto ).

Nautical .

to change the course of (a sailing vessel) to the opposite tack.

to navigate (a sailing vessel) by a series of tacks.

to equip (a horse) with tack.

Nautical .

to change the course of a sailing vessel by bringing the head into the wind and then causing it to fall off on the other side

He ordered us to tack at once.

(of a sailing vessel) to change course in this way.

to proceed to windward by a series of courses as close to the wind as the vessel will sail.

to take or follow a zigzag course or route.

to change one's course of action, conduct, ideas, etc.

to equip a horse with tack (usually fol. by up )

Please tack up quickly.

on the wrong tack

under a misapprehension; in error; astray

His line of questioning began on the wrong tack.

verb

detach , separate , unfasten , untack

noun

aim , alteration , approach , bearing , bend , deflection , deviation , digression , direction , double , echelon , heading , line , method , oblique course , path , plan , point of sail , procedure , set , shift , siding , sidling , sweep , swerve , switch , tactic , tangent , turn , variation , way , yaw , zigzag , brad , nail , point , pushpin , staple , thumbtack , attack , course , modus operandi , technique , twist

verb

add , affix , annex , append , baste , fasten , fix , hem , mount , nail , paste , pin , sew , staple , stitch , tag , tie