1. Make slack as by lessening tension or firmness
   "The captain ordered to slacken the sails";
   - remit
    
2. Become looser or slack
   "the rope slackened"
    
3. Become slow or slower
   "The pace slackened as fatigue set in";
   - slow, slow down, slow up, slack
    
4. Make less active or fast
   "He slackened his pace as he got tired";
   - slack, slack up, relax

Derived forms: slackening, slackens, slackened

See also: flag

Type of: decrease, lessen, loose, loosen, minify, weaken

Encyclopedia: Slacken