underactive

1 of 2

adjective

un·​der·​ac·​tive ˌən-dər-ˈak-tiv How to pronounce underactive (audio)
: characterized by an abnormally low level of activity
an underactive thyroid gland
underactivity
ˌən-dər-ak-ˈti-və-tē How to pronounce underactive (audio)
noun

underactivity

2 of 2

noun

: an abnormally low degree of activity
underactivity of thyroid gland

Examples of underactive in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Adjective
In people with depression, this area is underactive. — Emily Kay Votruba, EverydayHealth.com, 15 Dec. 2025 Based on these three levels, a doctor can determine whether the thyroid is underactive or overactive. — Melissa Rudy, FOXNews.com, 8 Dec. 2025 Thyroid dysfunction — whether overactive or underactive — also disrupts the hair growth cycle. — Ascend Agency, New York Daily News, 16 June 2026 Hypothyroidism is an underactive thyroid gland, and hyperthyroidism is an overactive thyroid gland. — Colleen Doherty, Verywell Health, 18 Dec. 2025 See All Example Sentences for underactive

Word History

Etymology

Noun

under entry 3 + activity

First Known Use

Adjective

1959, in the meaning defined above

Time Traveler
The first known use of underactive was in 1959

Rhymes for underactive

See All Rhymes for underactive

Browse Nearby Words

underaction
underactive
underactivity
See all Nearby Words

Cite this Entry

“Underactive.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/underactive. Accessed 8 Jul. 2026.

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Kids Definition

underactive

adjective
un·​der·​ac·​tive ˌən-də-ˈrak-tiv How to pronounce underactive (audio)
: having an abnormally low level of activity
an underactive gland

Medical Definition

underactive

adjective
un·​der·​ac·​tive -ˈak-tiv How to pronounce underactive (audio)
: characterized by an abnormally low level of activity
an underactive thyroid gland
underactivity
-ak-ˈtiv-ət-ē How to pronounce underactive (audio)
noun
plural underactivities
Last Updated: - Updated example sentences
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