Marked by calm self-control (especially in trying circumstances); unemotional:
— The most nerveless winner in the history of the tournament.

synonyms: cool, coolheaded.

Roget 158: powerless, impotent, unable, incapable, incompetent; inefficient, ineffective; inept; unfit, unfitted; unqualified, disqualified; unendowed; inapt, unapt; crippled, disabled etc. v.; armless^†.    harmless, unarmed, weaponless, defenseless, sine ictu [Lat.], unfortified, indefensible, vincible, pregnable, untenable.    paralytic, paralyzed; palsied, imbecile; nerveless, sinewless^†, marrowless^†, pithless^†, lustless^†; emasculate, disjointed; out of joint, out of gear; unnerved, unhinged; water-logged, on one's beam ends, rudderless; laid on one's back; done up, dead beat, exhausted, shattered, demoralized; graveled etc. (in difficulty) 704; helpless, unfriended^†, fatherless; without a leg to stand on, hors de combat [Fr.], laid on the shelf.    null and void, nugatory, inoperative, good for nothing; ineffectual etc. (failing) 732; inadequate etc. 640; inefficacious etc. (useless) 645.    ... show more

Polish: spokojny

Lacking strength:
— A weak, nerveless fool, devoid of energy and promptitude.

synonym: feeble.