voluntary

Adjective

• controlled by individual volition
  • voluntary motions
    
  • voluntary muscles
    

• of your own free will or design; done by choice; not forced or compelled
  • man is a voluntary agent
    
  • participation was voluntary
    
  • voluntary manslaughter
    
  • voluntary generosity in times of disaster
    
  • voluntary social workers
    
  • a voluntary confession
    

Noun

• composition (often improvised) for a solo instrument (especially solo organ) and not a regular part of a religious service or musical performance

• (military) a person who freely enlists for service

Related words

• Synonyms: 
  volunteer , military volunteer
• Antonyms: 
  involuntary , nonvoluntary , unvoluntary , draftee , conscript , inductee