Synonyms for tighten

verb

1. To make tight

   compress, condense, squeeze, bind, contract, strangle, constrict, crush, cramp, pinch, grip more tightly, clench, screw down, add pressure; see also stretch 2.

   Antonyms loosen*, relax, unloose.

2. To become tight

   contract, harden, congeal, stiffen, toughen, become more disciplined, become stricter.

   Antonyms melt, soften*, liquefy.