nerveless

(s) 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
coolheaded, cool,
(s) lacking strength
- "a weak, nerveless fool, devoid of energy and promptitude"- Nathaniel Hawthorne
feeble,

coolheaded cool feeble

nervelessly nervelessness