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1. Occurring or completed without perceptible delay: Relief was instantaneous.
2. Done or made as quickly or directly as possible: an instantaneous reply to my letter.
3. Present or occurring at a specific instant: instantaneous velocity; instantaneous pressure.

[From Medieval Latin īnstantāneus, from Latin īnstāns, īnstant-, present; see instant.]

in·stan′ta·ne′i·ty (ĭn-stăn′tə-nē′ĭ-tē, ĭn′stən-) n.
in′stan·ta′ne·ous·ly adv.
in′stan·ta′ne·ous·ness n.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.



(See also PACE, SPEEDING.)

at the drop of a hat At the slightest provocation; at once, promptly, without delay; immediately, instantly. In use since at least 1854, this expression is said to have derived from the early American frontier custom of dropping a hat to signal the beginning of a fight. The downward sweep of a hat has also been used to signal the start of races.

When in a bad temper [he was] ferocious and ready to quarrel “at the drop of a hat,” as the American saying goes. (M. Roberts, Western Avernas, 1887)

before you can say “Jack Robinson” Instantly, immediately. There are two common but equally unsubstantiated theories as to the origin of this phrase. One holds that a rather mercurial gentleman of that name was in the habit of paying such brief visits to neighbors that he was gone almost as soon as he had been announced. The other sees the source in these lines from an old, unnamed play:

A warke it ys as easie to be done As tys to saye, Jacke! robys on.

In popular use during the 18th century, the expression appeared in Fanny Bur-ney’s Evelina in 1778.

before you can say “knife” Very quickly or suddenly; before you can turn around. This colloquial British expression is equivalent to before you can say “Jack Robinson.” Mrs. Louisa Parr used it in Adam and Eve (1880).

in a jiffy In a trice, in a minute, right away. Although the exact origin of this expression is unknown, it is thought by some to be the modern spelling of the earlier gliff’a glimpse, a glance,’ and by extension ‘a short space of time, a moment.’ The phrase dates from the late 18th century.

They have wonderful plans for doing everything in a jiffy. (Charles Haddon Spurgeon, John Ploughman’s Pictures, 1880)

in a pig’s whisper In a short time; soon. A pig’s whisper was originally a short grunt, one so brief that it sounded almost like a whisper.

You’ll find yourself in bed, in something less than a pig’s whisper. (Charles Dickens, Pickwick Papers, 1837)

in two shakes of a lamb’s tail Immediately, right away; instantly. Although the exact origin is unknown, this expression is thought by some to be an enlargement of the older phrase in a brace or couple of shakes, which appeared in Richard H. Barham’s The In-goldsby Legends (1840). However, anyone familiar with sheep knows the quivering suddenness with which those animals twitch their tails.

one fell swoop All at once; with a single blow or stroke. The swoop of the phrase may carry its obsolete meaning of ‘blow,’ or refer to the sudden descent of a bird of prey; fell carries its meanings of ‘fierce, savage, destructive.’ Macduff uses the phrase in Shakespeare’s Macbeth when he learns that his wife, children, and servants have all been killed. In doing so, he plays on its associations with birds of prey:

All my pretty ones?
Did you say all? Oh Hellkite! All?
What, all my pretty chickens, and their dam
At one fell swoop? (IV, iii)

Contemporary usage does not restrict the phrase to serious contexts of fatal destruction; in fact, the expression is so often used lightly that it has generated the common spoonerism one swell foop.

on the double Instantly; without delay; right off the bat. This expression originated as military jargon for double-time marching. The term’s current civilian use is commonplace in the United States.

They came with me on the double. (James M. Cain, The Postman Always Rings Twice, 1934)

p.d.q. Immediately, at once. This widely used abbreviation of “pretty damn quick” was coined in 1867 by Don Maginnis, a Boston comedian.

He changed her mind for her p. d. q. (John O’Hara, The Horse Knows the Way, 1964)

right off the bat Immediately; at once; instantaneously. This very common expression is of obvious baseball origin.

You can tell right off the bat that they’re wicked, because they keep eating grapes indolently. (The New Yorker, May, 1955)

The less frequently heard synonymous right off the reel may derive from the specific sports use of reel in fishing, though many of the more general uses of reel could account equally well for its origin.

Picturesque Expressions: A Thematic Dictionary, 1st Edition. © 1980 The Gale Group, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.instantaneousness - the quickness of action or occurrence; "the immediacy of their response"; "the instancy of modern communication"
celerity, rapidity, rapidness, speediness, quickness - a rate that is rapid
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in classic literature ?
Nor could it guess the toughness of the fiber of the flesh, the instantaneousness of the cell explosions of the muscles, the fineness of the nerves that wired every part of him into a spendid fighting mechanism.
describing the "one moment," singularity and instantaneousness
The logarithmic increase in channels of expression, access to which is now open to everyone without any restriction or regulation, the instantaneousness of exchanges that opens the floodwaters to the spontaneous expression of feelings without giving a moment's reflection, the acceleration of time that only leaves people wanting more, the resulting obligation to present any idea or information as briefly as possible--with the Tweet being the incarnation par excellence of this norm--all of this contributes to the reduction of public debate to the circulation of "sound bites." These sound bites are meant to connect directly with a target audience through a simple formula designed to impress on all that mediated existence is everything; that there is nothing outside of sound bites.
The instantaneousness of a masked (previously un-masked) or non-masked (previously masked) appearance from an unseen position creates a moment equally pivotal to that created by a witnessed masking or un-masking in full view of the audience.
The approach isn't entirely unexpected in a country where people are obsessed with the instantaneousness of technology but don't have the patience to understand the science behind it.
It can be a different thing in public hospitals, but in private ones, it happens that patients expect care to be served with all the smiling humility-dare I say sycophancy-of a five-star hotel concierge, with all the instantaneousness of a precooked McDonald's burger.
(29) The Greek verb horizo, from which "horizon" is derived, means precisely "to delimit." Crell has claimed that Heidegger must have taken the notion of ecstatic temporality from Aristotle's explication of the concept of instantaneousness (to exaiphnes) in the Physics (4.13.222b15-21), where Aristotle says, among other things, that change is in itself a "departure" (ekstatikon); David Farell Crell, Intimations of Mortality (State College: The Pennsylvania State University Press, 1991), 49-50.
Due to the instantaneousness and ferocity of the HST impact load, the failure mode of the joint bolt in this study is considered as instant complete damage.
Thus the interest of this essay is to look at the works that were produced through the flexibility of the photocopier and the ready-to-go impulsivity and instantaneousness that the machine offered.
THE modern world may have us convinced that speed and instantaneousness are everything, but it's when we slow down that we usually find the greatest rewards.