un·​der·​weight | \ˌən-dər-ˈwāt \

Definition of underweight 

(Entry 1 of 2)

: weight below normal, average, or requisite weight



Definition of underweight (Entry 2 of 2)

: weighing less than the normal or requisite amount

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Synonyms & Antonyms for underweight

Synonyms: Adjective

featherlight, feathery, light, lightweight, weightless

Antonyms: Adjective

heavy, hefty, leaden, overweight, ponderous, weighty

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Examples of underweight in a Sentence


the long illness left him frail and underweight

Recent Examples on the Web: Noun

On Tuesday, Snapchat's lead underwriter Morgan Stanley downgraded Snap from equal weight to underweight and cut its price target to $16 from $28. Krishna Thakker, Fortune, "Here’s How Many Billions Evan Spiegel Has Lost Since Snap’s IPO," 12 July 2017

Recent Examples on the Web: Adjective

The latest report found that mothers in India were more likely to deliver underweight babies in households that used wood or dung as cooking fuel. Umair Irfan, Vox, "Why India’s air pollution is so horrendous," 31 Oct. 2018 The children ages 2 to 29 were mostly pale and severely underweight, they hadn't bathed for months and the house reeked of human waste. Brian Melley, Fox News, "Prosecutor: Abused kids upbringing like 'Lord of the Flies'," 22 June 2018 As the adoption dragged on, Boyle said Ngoty was severely underweight, with fever, mouth sores and a fungal rash on her scalp. Maria Sacchetti, Washington Post, "She coached her team to the NCAA tournament. Then she quit, for her daughter.," 28 Mar. 2018 At the time, ranchers were required to remove any dead animals and undertake just one additional preventive measure from a menu of options, which could be as basic as not turning out to pasture underweight calves that could be easier targets. New York Times, "Who’s Afraid of the Big Bad Wolf Scientist?," 5 July 2018 His German shepherd Nala was found abandoned and severely underweight in an apartment in Azusa after the residents left. Hillary Davis, latimes.com, "Coming to the rescue: Newport resident’s dog food company starts nonprofit to get homeless dogs veterinary care," 7 July 2018 America Inc is similarly underweight in the rest of Asia, but there is much less fighting talk about South Korea or Japan. The Economist, "America Inc and the rage against Beijing," 28 June 2018 The report relies on data mostly from 2016, the most recent available, on 16 indicators of well-being, from the highest education level attained by their parents to the percentage of underweight infants to how many teens abuse drugs and alcohol. Kate Santich, OrlandoSentinel.com, "Florida's kids see gains in economic well-being, but gaps persist for children of color," 27 June 2018 In this study, people with BMIs between 22 and 23 had the lowest risk for cardiovascular disease events (e.g. heart attacks), and those with BMIs of 18.5 or lower (classified as underweight) had a higher risk of cardiovascular disease. Sarah Jacoby, SELF, "The Science on Weight and Health," 26 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'underweight.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of underweight


1596, in the meaning defined above


1675, in the meaning defined above

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Time Traveler for underweight

The first known use of underweight was in 1596

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More Definitions for underweight



English Language Learners Definition of underweight

: weighing less than the normal or expected amount : too light


un·​der·​weight | \ˌən-dər-ˈwāt \

Kids Definition of underweight

: weighing less than what is normal, average, or necessary


un·​der·​weight | \-ˈwāt \

Medical Definition of underweight 

: weighing less than the normal amount for one's age, height, and build underweight children underweight adults typically have a body mass index of less than 18.5

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by force of circumstances

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