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1. The ordinal number matching the number quadrillion in a series.
2. One of a quadrillion equal parts.

quad·ril′lionth adv. & adj.
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.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.quadrillionth - one part in a quadrillion equal parts
common fraction, simple fraction - the quotient of two integers
Adj.1.quadrillionth - the ordinal number of one quadrillion in counting order
ordinal - being or denoting a numerical order in a series; "ordinal numbers"; "held an ordinal rank of seventh"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
A laser that pulses at one quadrillionth of a second has been used in the UK for the first time.
A spokesman for University Hospital Southampton (UHS) said: "Known as the Femto LDV Z8, it pulses at one quadrillionth of a second and is so precise it can cut the cornea into different planes which can be used to treat a number of different eye diseases."
Due to its short pulses--lasting one quadrillionth of a second--a femtosecond laser can vaporise material precisely, without heating the surrounding matter.
The new system is based on a femtosecond (one quadrillionth of a second) streak camera and integrated a data acquisition type used in applications like tomography.
With our new system, you can selectively look in a desired direction and at a very small part of the picture in front of you at any given time, by controlling the timing with femto-second -- quadrillionth of a second -- precision," says Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering in the Division of Engineering and Applied Science at Caltech, and the principal investigator of a paper describing the new camera.
The new camera technology opens up many possibilities, especially for scientists - natural processes taking place in a trillionth or even a quadrillionth of second can now be captured on tape.
The new laser achieves 35 femtosecond pulses (a femtosecond is one quadrillionth of a second) at a wavelength of 800 nanometers.
With the leap in laser technology from pulse duration measured in nanoseconds (1 billionth of a second) to one measured in femtoseconds (1 quadrillionth of a second) new vistas opened in the practice of cataract surgery.
(A femtosecond is one quadrillionth of a second.) The breakthrough makes it possible to probe the ultra-fast motions that are involved in overcoming activation energy barriers to drive chemical reaction, including complex ones like protein folding.
In water, each bond lasts only one 100 quadrillionth of a second (Curtis, 1983), yet so many are being formed and broken at any given instant that they cause the water molecules in a drop of water to cling together with considerable strength and yet to resist clinging together further, even when pressure is applied to them.
(However, it is given as a main entry in our 1998 printing of Webster's New Collegiate Dictionary, 10th edition, where it is defined as one quadrillionth of a second.)