1 [transitive always + adverb/preposition]
to attach something to a wall, board etc, using a tack
tack something to something
A handwritten note was tacked to the wall.
to change the course of a sailing ship so that the wind blows against its sails from the opposite direction
to fasten pieces of cloth together with long loose stitches, before sewing them
tack something ↔ onphrasal verb
a beautiful old house with a hideous modern extension tacked on at the back