slack·​en ˈsla-kən How to pronounce slacken (audio)
slackened; slackening ˈsla-kᵊn-iŋ How to pronounce slacken (audio)

transitive verb

: to make less active : slow up
slacken speed at a crossing
: to make slack (as by lessening tension or firmness)
slacken sail

intransitive verb

: to become slack or slow or negligent : slow down
: to become less active : slack
Choose the Right Synonym for slacken

delay, retard, slow, slacken, detain mean to cause to be late or behind in movement or progress.

delay implies a holding back, usually by interference, from completion or arrival.

bad weather delayed our arrival

retard suggests reduction of speed without actual stopping.

treatment that retards tumor growth

slow and slacken also imply a reduction of speed, slow often suggesting deliberate intention

she closed her eyes and slowed her breathing

, slacken an easing up or relaxing of power or effort.

on hot days runners slacken their pace

detain implies a holding back beyond a reasonable or appointed time.

unexpected business had detained her

Examples of slacken in a Sentence

Sales show no sign of slackening. As he began to relax, his grip on the steering wheel slackened. The captain ordered us to slacken the sails.
Recent Examples on the Web That restless buildup for the perfect tomato to slacken and blush, to actually smell of fire and rain? Eric Kim, New York Times, 19 July 2023 Smoke concentration might increase Wednesday and Thursday as winds are predicted to slacken, according to the MDE, which monitors air quality throughout the state. Dan Belson, Baltimore Sun, 6 June 2023 But in the video, Jackson’s lips started to slacken around the pacifier and change color, Higgins said. Jessica Bartlett,, 29 Apr. 2023 Winds may slacken a bit overnight, but gradients will tighten again Friday and strong winds gusts will ramp up again. oregonlive, 17 Nov. 2022 But as the fleet reached Canvey Island, the already light winds slackened, and the race committee shortened the course. William Booth, Washington Post, 24 July 2023 Possibly the same could be said of Ms. Kawakubo who, like Picasso in his 80s, shows little sign of slackening pace. Guy Trebay, New York Times, 28 June 2023 Then Portland will see showers slacken off through the afternoon. oregonlive, 5 Apr. 2023 Confidence: Medium Tomorrow night: Easterly and northeasterly breezes may not slacken much. A. Camden Walker, Washington Post, 28 May 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'slacken.' 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

14th century, in the meaning defined at transitive sense 1

Time Traveler
The first known use of slacken was in the 14th century

Dictionary Entries Near slacken

Cite this Entry

“Slacken.” Dictionary, Merriam-Webster, Accessed 22 Sep. 2023.

Kids Definition


slack·​en ˈslak-ən How to pronounce slacken (audio)
slackened; slackening -(ə-)niŋ How to pronounce slacken (audio)
: to make or become slower or less energetic
slacken speed
: to make less taut : loosen
slacken sail
: to become careless

More from Merriam-Webster on slacken

Last Updated: - Updated example sentences
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