slacken

Verb

• make slack as by lessening tension or firmness

• become looser or slack
  • the rope slackened
    

• make less active or fast
  • He slackened his pace as he got tired
    
  • Don't relax your efforts now
    

• become slow or slower
  • Production slowed
    

Related words

• Synonyms: 
  remit , slack , slack up , relax , slow , slow down , slow up