underweight

1 of 2

noun

un·​der·​weight ˌən-dər-ˈwāt How to pronounce underweight (audio)
Synonyms of underweightnext
: weight below normal, average, or requisite weight

underweight

2 of 2

adjective

: weighing less than the normal or requisite amount

Synonyms of underweight

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Adjective

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Examples of underweight in a Sentence

Adjective the long illness left him frail and underweight
Recent Examples on the Web
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Adjective
People were still underweight and, certainly in other parts of Europe, really feeling the pinch. — Kat Chen, Condé Nast Traveler, 27 Oct. 2026 The district attorney’s office said the child was reported to smell like cat urine and appeared seriously underweight and pale. — Los Angeles Times, 14 Oct. 2026 About two-thirds of Gaza’s people are thought to be malnourished; as many as seven in ten babies are born underweight. — Dexter Filkins, New Yorker, 14 Sep. 2026 The study also found a particularly high mortality risk among older adults who were underweight. — Faye Chiu, CNN Money, 26 Aug. 2026 See All Example Sentences for underweight

Word History

First Known Use

Noun

1596, in the meaning defined above

Adjective

1675, in the meaning defined above

Time Traveler
The first known use of underweight was in 1596

Rhymes for underweight

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Browse Nearby Words

under weigh
underweight
underwhelm
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Cite this Entry

“Underweight.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underweight. Accessed 1 Nov. 2026.

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Kids Definition

underweight

adjective
un·​der·​weight
ˌən-dər-ˈwāt
: weighing less than what is normal, average, or necessary

Medical Definition

underweight

adjective
un·​der·​weight -ˈwāt How to pronounce underweight (audio)
: 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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