nerveless in WordNet English dictionary

1. 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"
   cool  coolheaded  nerveless 
   
2. lacking strength
   "a weak, nerveless fool, devoid of energy and promptitude"- Nathaniel Hawthorne
   feeble  nerveless