Temerity and similar words

Temerity 

|təˈmeritē|noun

excessive confidence or boldness;

audacity : no one had the temerity to question his conclusions.

ORIGIN late Middle English : from Latin temeritas, from temere‘rashly.

‘THE RIGHT WORD

The line that divides boldness from foolishness or stupidity is often a fine one.

Someone who rushes hastily into a situation without thinking about the consequences might be accused of rashness,

while temerity implies exposing oneself needlessly to danger while failing to estimate one’s chances of success (: she had the temerity to criticize her teacher in front of the class).

Audacity describes a different kind of boldness, one that disregards moral standards or social conventions (: he had the audacity to ask her if she would mind paying for the trip).

Someone who behaves with foolhardiness is reckless or downright foolish (: climbing the mountain after dark was foolhardiness and everyone knew it),

while impetuosity describes an eager impulsiveness or behavior that is sudden, rash, and sometimes violent ( | his impetuosity had landed him in trouble before).

Gall and effrontery are always derogatory terms. 

Effrontery is a more formal word for the flagrant disregard of the rules of propriety and courtesy (: she had the effrontery to call the president by his first name),

while gall is more colloquial and suggests outright insolence ( | he was the only one with enough gall to tell the boss off).