dilation

noun

di·​la·​tion dī-ˈlā-shən How to pronounce dilation (audio)
plural dilations
: the act or action of enlarging, expanding, or widening : the state of being dilated: such as
a
: the act or process of expanding (such as in extent or volume)
… the dilation of palladium grains undergoing hydrogen absorption.Frédéric Favier et al.
The thermometer bulbs are subject to thermal and pressure dilationLeslie A. Guildner
b
: the act or action of stretching, widening, or enlarging an organ or part of the body
dilation of the pupil with atropine
Faced with threatening situations, the body responds with a sudden dilation of blood vessels.Paul G. Donohue
She has been treated with esophageal dilation, antacids and cimetidine …David B. Adams
This year in the United States, more than 200,000 balloon dilations of the coronary arteries will be done …John Stone
c
: the condition of being stretched or enlarged beyond normal dimensions : dilatation sense 1a
chronic dilation of arterioles
left ventricular dilation
While the physiological cause of migraines is still unclear, researchers suspect that it involves the prolonged dilation of blood vessels in the brain.Andrew Weil
d
: an increase in duration of an event due to the effects of special relativity (see relativity sense 3a)
However, if the Sun kept its same mass and were made smaller in circumference so its surface was closer to its center, then its gravity would be stronger, and correspondingly its gravitational time dilation—its warpage of time—would become larger.Kip S. Thorne
A related "time dilation" is caused by gravity: near a large mass, clocks tend to run slow.Martin Rees

Examples of dilation in a Sentence

Recent Examples on the Web Possible reasons include lying down or sleeping, a slowing down of contractions, contractions without dilation, or the baby not descending, despite contractions still occurring. Parents Editors, Parents, 4 Mar. 2024 In 2019, Indiana’s legislature outlawed dilation and evacuation, or D. & E., a procedure commonly used by doctors in the second trimester, when some major genetic or anatomic anomalies can first be detected and other complications may arise. Peter Slevin, The New Yorker, 25 Feb. 2024 Caffeine is a vasoconstrictor, which may help reverse the dilation done by alcohol. Delaney Nothaft, USA TODAY, 19 Jan. 2024 This blood vessel dilation explains why your ears get red and painful in the cold. Max G. Levy, WIRED, 6 Jan. 2024 Misoprostol, taken second, is a synthetic prostaglandin (a hormone-like substance) that induces contractions and cervical dilation. Beth Mole, Ars Technica, 19 Apr. 2023 Some arrived for overnight dilations ahead of surgical abortions; most were medical or pill terminations. Amy Pedulla, STAT, 14 Dec. 2023 That’s enough to deduce details about a user’s eyes, including the direction of their gaze, their eye position in relation to the screen, and the dilation of their pupils. IEEE Spectrum, 13 Dec. 2023 This means that the pain occurs due to the dilation and swelling of blood vessels. Carla Delgado, Discover Magazine, 11 Aug. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'dilation.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

circa 1598, in the meaning defined above

Time Traveler
The first known use of dilation was circa 1598

Dictionary Entries Near dilation

Cite this Entry

“Dilation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/dilation. Accessed 19 Mar. 2024.

Kids Definition

dilation

noun
di·​la·​tion dī-ˈlā-shən How to pronounce dilation (audio)
1
: the act of dilating : the state of being dilated : expansion
dilation of the pupils of the eyes
2
: the action of stretching or enlarging an organ or part of the body

Medical Definition

dilation

noun
di·​la·​tion dī-ˈlā-shən How to pronounce dilation (audio)
1
a
: the state of being dilated
monitored cervical dilation
b
: the act or action of stretching, widening, or enlarging an organ or part of the body
dilation of the pupil with atropine
2
: the condition of being stretched or enlarged beyond normal dimensions : dilatation sense 1a
chronic dilation of the arterioles
left ventricular dilation

More from Merriam-Webster on dilation

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