Temerity

(n.) Unreasonable recklessness; extreme venturesomeness; rashness; as, the temerity of a commander in war.

Thesaurus Entries

assurance, audacity, brashness, brass, brazen boldness, cheek, chutzpah, daring, foolhardiness, gall, hardihood, hardiness, heedlessness, heroics, hubris, impertinence, impetuosity, improvidence, imprudence, impudence, indiscretion, injudiciousness, insolence, intrusiveness, nerve, overboldness, overcarelessness, overconfidence, oversureness, overweeningness, precipitateness, rashness, recklessness, temerariousness, unchariness, unwariness, venturesomeness