• temerarious (adj.): reckless; rash; (adv.): temerariously; (n.): temerariousness. [1525-35; from Latin temerārius; from temer(e), ‘blindly’, ‘heedlessly’ + -ārius, -ary]. ~ (Webster’s College Dictionary).

• temerarious (adj.): characterised by unthinking boldness and haste; (synonyms): brash, foolhardy, harum-scarum, hasty, headlong, hotheaded, ill-considered, impetuous, improvident, impulsive, incautious, madcap, precipitant, precipitate, rash, reckless, slapdash, unconsidered. ~ (American Heritage Roget’s Thesaurus).

• temerarious (adj.): presumptuously or recklessly bold; rash or reckless; [e.g.]: “I would never have been temerarious enough to make use of such a title on my own”. (Brendan Gill); (adv.): temerariously; (n.): temerariousness; (synonyms): reckless, rash¹, foolhardy, temerarious; these adjectives mean given to or marked by unthinking boldness; reckless suggests wild carelessness and disregard for consequences; [e.g.]: “conceiving measures to protect the fur-bearing animals from reckless slaughter”. (Gertrude Atherton); rash implies haste, impetuousness, and insufficient consideration; [e.g.]: “Take calculated risks. This is quite different from what being rash is”. (General George S. Patton); foolhardy implies injudicious or imprudent boldness; [e.g.]: “a foolhardy attempt to wrest the gun from the mugger”; temerarious suggests reckless presumption; [e.g.]: “this temerarious foeman who dared intervene between himself [the elephant] and his intended victim”. (Edgar Rice Burroughs). [from Latin temerārius, from temere, ‘rashly’]. ~ (American Heritage Dictionary).

• temerarious† (adj.): heedless or careless of consequences; unreasonably venturous; reckless; headstrong; inconsiderate; rash; careless; [e.g.]: “I spake against temerarious judgment”. (Bishop Hugh Latimer, “Fourth Sermon before Edward VI.”; 1549). [= French téméraire = Spanish, Portuguese, Italian temerario, from Latin temerarius, ‘something which happens by chance’, ‘imprudent’, from temere, ‘by chance’, ‘at random’, ‘rashly’: see temerity, temerous]. ~ (Century Dictionary and Cyclopaedia).

• temerarious (adj.): marked by temerity; rashly or presumptuously daring; [e.g.]: “it was a temerarious comment”; “those temerarious people rush in without forethought”; (adv.): temerariously; (n.): temerariousness; (synonyms): audacious; brash; daredevil; foolhardy; madcap; overbold; overconfident; reckless. [etymology: Latin temerarius , from temere ; first known use; 1532, in the meaning defined above; temerarious is related to the somewhat more common word temerity; the word temerarious was borrowed into English in the early sixteenth century from Latin temerarius, which in turn derives from Latin temere, ‘blindly’, ‘recklessly’; the word temerity, which arrived in English over a century earlier, also derives from temere; another descendant is the rare word intemerate⁽*⁾, ‘pure’, ‘undefiled’; temere itself is akin to Old High German demar, Latin tenebrae, and Sanskrit tamas, all of which have associations with darkness]. ~ (Merriam-Webster Dictionary).

⁽*⁾intemerate (adj.): inviolate, pure, undefiled. [Latin intemeratus, from in - + temeratus, past participle of temerare, ‘to violate’, ‘defile’, from temere, ‘rashly’, ‘by chance’]. ~ (Merriam-Webster Dictionary).

• temerariously† (adv.): in a temerarious or presumptuous manner; rashly; inconsiderately; [e.g.]: “It asserts and enacts so they have no right, as they temerariously presume, and usurpedly⁽*⁾ take on themselves, to be parcel of the body, in manner claiming how without their assents nothing can be enacted at any parliament within this land”. (Henry Hallam; “Constitutional History of England”, III). ~ (Century Dictionary and Cyclopaedia).

⁽*⁾usurpedly (adv.; rare): by an act or acts of usurpation; in a manner characterised by usurpation; (viz.: the act of usurping; the act of seizing or occupying and enjoying the place, power, functions, or property of another without right; especially, the wrongful occupation of a throne: as, the usurpation of supreme power). ~ (Century Dictionary and Cyclopaedia).

• temeration† (n.): contamination; profanation; pollution; [e.g.]: “Those cryptic ways of institution by which the ancients did hide a light, and keep it in a dark lantern from the temeration of ruder handlings and popular preachers”. (Jeremy Taylor, “Works”; ed. 1835, II. 121). [from Late Latin temeratio(n-), ‘a dishonouring’ or ‘profaning’, from Latin temerare , pp. temeratus, ‘violate’, ‘pollute’, lit. ‘treat rashly’, from temere, ‘rashly’, ‘at random’]. ~ (Century Dictionary and Cyclopaedia).

• temerous (adj.; rare): heedless; rash; reckless; [e.g.]: “A temerous tauntress who delights in toys”. (Uncertain Authors, “Against an Unstedfast Woman”); “I have not the temerous intention of disputing for a moment”. (Atlantic Monthly, LXI. 281). [from Medieval Latin temerus , developed after the analogy of other adjectives as related to adverbs in -c, from Latin temere , ‘by chance’, ‘rashly’: see temerity, temerarious]. ~ (Century Dictionary and Cyclopaedia).

• temerously (adv.; rare): heedlessly; rashly; recklessly; [e.g.]: “Though I do not temerously diffine anything to come”. (Bishop Bale, “Image”, ii. fol. 69). ~ (Century Dictionary and Cyclopaedia).

• temerity (n.): extreme venturesomeness; rashness; recklessness; [e.g.]: “The temerity which risked the fate of an empire on the chances of a single battle”. (Henry Hallam, “Middle Ages”, i. 4); “It appears to me I cannot, without exposing myself to the charge of temerity, seek to discover the [impenetrable] ends of Deity”. (René Descartes, “Meditations”; tr. by John Veitch, iv); (synonyms): rashness, temerity (see rashness); venturesomeness, presumption, foolhardiness. [= French témérité = Provençal temeritat = Spanish temeridad = Portuguese temeridade = Italian temcrità, from Latin temerita (t-)s, ‘chance’, ‘accident’, ‘rashness’, from temere, ‘by chance’, ‘casually’, ‘rashly’; cf. temerous]. ~ (Century Dictionary and Cyclopaedia).