gratuitous

Adjective

• unnecessary and unwarranted
  • a strikers' tent camp...was burned with needless loss of life
    

• costing nothing
  • complimentary tickets
    
  • free admission
    

• without cause
  • a gratuitous insult
    

Related words

• Synonyms: 
  needless , uncalled-for , complimentary , costless , free , gratis(p)