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

tril′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.trillionth - one part in a trillion equal parts
common fraction, simple fraction - the quotient of two integers
Adj.1.trillionth - the ordinal number of one trillion 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 ?
This cooling cinder called Earth, spinning in the darkness at the back of beyond, is a minor speck of residue from the Big Bang, which lasted less than a billionth of a trillionth of a trillionth of a second 13.8 billion years ago.
A SUPER-STRONG laser can heat water to 1,000 times boiling point in just a trillionth of a second.
It's a feat that requires incredible precision: Force is typically measured in newtons--the amount of force needed to accelerate one kilogram of mass one meter per second squared--but Zhu's technique measures on a scale of piconewtons--that is, one trillionth of a newton.
The whole process, in real time takes one trillionth of a second.
The four-neutron nuclei lasted about a billionth of a trillionth of a second before decaying into other particles.
Researchers aim to detect any relative motion between the two masses to within a few picometers (a trillionth of a meter or [10.sup.-12] m).
"Combined with theoretical calculations, these data show how the light pulses generate wrinkles that have large amplitudes -- more than 15 percent of the layer's thickness -- and develop extremely quickly, in about a trillionth of a second.
Attempts to "square the circle" yield a parade of more exact calculations through history to Shiguro Kondo's calculation of pi's trillionth decimal place in 2011 using a home computer.
Finding the particle - often referred to as the "God particle" - required teams of thousands of scientists and mountains of data from trillions of colliding protons in the world's biggest atom smasher - CERN's Large Hadron Collider - which produces energies simulating those one trillionth to two trillionths of a second after the Big Bang.
The collider recreated a very small model of the state of the universe as it was in the first trillionth of a second after the Big Bang.
One researcher calculates that trillionth ton will be released by 2040.
Ordinarily optical switches respond at rate of a few picoseconds around a trillionth of a second.