underweight

1 of 2

noun

un·​der·​weight ˌən-dər-ˈwāt 

: weight below normal, average, or requisite weight

underweight

2 of 2

adjective

: weighing less than the normal or requisite amount

Synonyms of underweight

Adjective

• lightweight

Examples of underweight in a Sentence

Adjective

the long illness left him frail and underweight

Recent Examples on the Web

Adjective

Authorities said many of the dogs suffered from severe flea infestation, and some of the pups were underweight. — Leonard Greene, New York Daily News, 19 June 2026

Upon arrival, several of them were in critical condition and others were underweight with digestive issues. — Richard Tribou, The Orlando Sentinel, 16 June 2026

Looking beyond Taiwan Ken Wong, Asia equity portfolio specialist at Eastspring Investments, is underweight Taiwan, and overweight South Korea. — Michael Considine, CNBC, 16 June 2026

The assistant medical examiner testified that the child was only 19 pounds, which was considered underweight for her age and height. — Ashley Paul, CBS News, 4 June 2026

Word History

First Known Use

Noun

1596, in the meaning defined above

Adjective

1675, in the meaning defined above

Rhymes for underweight

• abdicate
• abrogate
• acetate
• activate
• actuate
• aggravate
• agitate
• alginate
• alienate
• allocate
• amputate
• angulate

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 

: 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