imperturbable

comparative more imperturbable · superlative most imperturbable

1. Not capable of being, or not easily, perturbed, excited, or upset; calm and collected, even under pressure.

   [T]he good Dominie bore all his disasters with gravity and serenity equally imperturbable. "Prodi-gi-ous!" was the only ejaculation they ever extorted from the much-enduring man.

   1815 February 24, [Walter Scott], chapter VIII, in Guy Mannering; or, The Astrologer. […], volume I, Edinburgh: […] James Ballantyne and Co. for Longman, Hurst, Rees, Orme, and Brown, […]; and Archibald Constable and Co., […], →OCLC, page 116

   4 more examples

   [T]o a vviſe man there can happen no iniury or offence at all, to moleſt the felicity of his minde, vvhich (in the Stoicks opinion) ought to bee imperturbable, and his heart adamantine.

   1605, Giacomo Affinati d’Acuto Romano, chapter 23, in A[nthony] M[unday], transl., The Dumbe Divine Speaker, or: Dumbe Speaker of Diuinity. […], London: […] [R. Bradock] for William Leake, […], →OCLC, page 257

   In the meanwhile, Sir Piercie Shafton sate still as a stone on the chair in which he had deposited himself, […] his eyes cast up to the ceiling as if he had meant to count every mesh of cobweb with which the arched roof was canopied, wearing at the same time a face of as solemn and imperturbable gravity, as if his existence had depended on the accuracy of his calculation.

   1820 March, [Walter Scott], chapter II, in The Monastery. A Romance. […], volume II, Edinburgh: […] Longman, Hurst, Rees, Orme, and Brown, […]; and for Archibald Constable and Co., and John Ballantyne, […], →OCLC, pages 60–61

   "We may keep it by us," replied the pawnbroker, "for months; there is no demand for such articles." "But," exclaimed she, eagerly, "I shall soon redeem it!" "So you all say," returned the man, with imperturbable coolness.

   1837, L[etitia] E[lizabeth] L[andon], “Poverty”, in Ethel Churchill: Or, The Two Brides. […], volume III, London: Henry Colburn, […], →OCLC, page 280

   This sort of thing is meat and drink to the born Controller—and Controllers are born with the right imperturbable temperament for the job; hence the fact that they are recruited from many different grades of operating staff, and some recruits don't stay the course.

   1962 August, G[eoffrey] Freeman Allen, “Traffic Control on the Great Northern Line”, in Modern Railways, Shepperton, Surrey: Ian Allan Publishing, →ISSN, →OCLC, page 132

   Synonyms: cool-headed, unexcitable, unperturbable, calm, steady, collected, composed, cool-headed · Antonyms: perturbable, atrabilious, bad-tempered, bilious, bitchy, brainish, cantankerous, carnaptious