Definition of "instantaneous"

This instantaneous motion is supposed by you, to be infinitely swift.

1631, William Twisse, chapter VI, in A Discovery of D. Iacksons vanitie, page 223

However, no lovers in romance ever cemented a more inſtantaneous friendſhip.

1766, [Oliver Goldsmith], “Fresh Mortifications, or a Demonstration that Seeming Calamities may be Real Blessings”, in The Vicar of Wakefield: […], volume I, Salisbury, Wiltshire: […] B. Collins, for F[rancis] Newbery, […]; reprinted London: Elliot Stock, 1885, page 137

The colour now rushed into Elizabeth's cheeks in the instantaneous conviction of its being a letter from the nephew, instead of the aunt; [...]

1813 January 27, [Jane Austen], chapter XV, in Pride and Prejudice: […], volume III, London: […] [George Sidney] for T[homas] Egerton, […], page 262

I walk always with my right hand closed round the india-rubber ball which I have in my trouser pocket. The pressing of this ball actuates a detonator inside the flask I carry in my pocket. It's the principle of the pneumatic instantaneous shutter for a camera lens.

1906 January–October, Joseph Conrad, chapter IV, in The Secret Agent: A Simple Tale, London: Methuen & Co., […], published 1907; The Secret Agent: A Simple Tale (Collection of British Authors; 3995), copyright edition, Leipzig: Bernhard Tauchnitz, 1907, pages 68–69

The penis is the perfectly obvious and natural symbol of instantaneous time.

1981, William Irwin Thompson, The Time Falling Bodies Take to Light: Mythology, Sexuality and the Origins of Culture, London: Rider/Hutchinson & Co., page 129

He said that the bullet went through her head, severed her spine and death would have been almost instantaneous.

2007 May 30, “Spector jury given graphic account of actress ‘murder’”, in The Times‎, London, retrieved 13 July 2007