nerveless

Adjective

• lacking strength
  • a weak, nerveless fool, devoid of energy and promptitude- Nathaniel Hawthorne
    

• marked by calm self-control (especially in trying circumstances); unemotional
  • play it cool
    
  • keep cool
    
  • stayed coolheaded in the crisis
    
  • the most nerveless winner in the history of the tournament
    

Related words

• Synonyms: 
  feeble , cool , coolheaded