un·​der·​weight | \ ˌən-dər-ˈwāt How to pronounce underweight (audio) \

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

In a 2017 investigation, National Geographic found an anteater slurping up pink yogurt, an underweight manatee being fed soy milk with a baby bottle, and sloths—which sleep 22 hours a day in the wild—being passed around among excited tourists. Kirsten Luce, National Geographic, "How one Amazon community is trying to move on from illegal wildlife tourism," 15 Aug. 2019 The three sisters were shy, slightly underweight, and excessively dirty with some skin issues, Kennedy said. Maria Lovato, BostonGlobe.com, "Three pit bull mix puppies found in Jamaica Plain cemetery," 24 July 2019 All were underweight, and Gudami bore shrapnel scars on his head. New York Times, "‘Her Eyes Were Full of Fear.’ Turkey Repatriates Children of ISIS Followers.," 27 July 2019 She is being fed 15 times a day and now weighs around 65 pounds, but Nantarika says Mariam is still a bit underweight. Brigit Katz, Smithsonian, "Friendly Baby Dugong Becomes Conservation Symbol in Thailand," 3 July 2019 Black women in New Jersey are three-and-a-half times more likely to die from pregnancy or birth complications than their white counterparts, and their babies are at a much higher risk of being born underweight or dying before their first birthday. Chloe Angyal, Marie Claire, "Cory Booker Gets Real About Reproductive Justice," 20 June 2019 The exact dose of vacuum energy, the precise mass of our underweight Higgs boson, and other anomalies must have high odds within the subset of habitable universes. Quanta Magazine, "In a Multiverse, What Are the Odds?," 3 Nov. 2014 Alaska had the nation’s lowest rate of babies born dangerously underweight in 2017, but the highest rate of child and teenage deaths, according to the latest installment of the Kids Count report that measures how children and teens are faring. Tegan Hanlon, Anchorage Daily News, "Alaska ranks 45th in the nation for children’s well-being, report says," 18 June 2019 Some of them are expensive coffee-table books that weigh about 6 pounds—that’s the weight of a slightly underweight newborn. Liana Satenstein, Vogue, "Sorry Marie Kondo—I Love Mess!," 12 Feb. 2019

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 How to pronounce underweight (audio) \

Kids Definition of underweight

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


un·​der·​weight | \ -ˈwāt How to pronounce underweight (audio) \

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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