estrus

noun

es·​trus ˈe-strəs How to pronounce estrus (audio)
: a regularly recurrent state of sexual receptivity during which the female of most mammals will accept the male and is capable of conceiving : heat
Some mares will exhibit estrus for 15 to 20 days.—Frederick Harper
also : a single occurrence of this state

Examples of estrus 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.
During the rut, bucks might even push estrus does into such areas to get them away from rival bucks. — Josh Honeycutt, Outdoor Life, 14 Nov. 2024 Festo talks me through the drama as the bull ignores the matriarch to diligently sniff for a female in estrus. — Saumya Ancheri, Condé Nast Traveler, 4 Apr. 2022 So as part of managing this, female giraffes may be given a daily dose of liquid birth control to keep them from cycling into estrus during certain time periods. — Jim Higgins, jsonline.com, 8 July 2025 Fortunately, Willow was not in estrus, preventing an unwanted pregnancy, but the incident still resulted in a costly emergency visit. — Lydia Patrick, Newsweek, 18 Mar. 2025 See All Example Sentences for estrus

Word History

Etymology

New Latin, from Latin oestrus gadfly, frenzy, from Greek oistros — more at ire

First Known Use

circa 1890, in the meaning defined above

Time Traveler
The first known use of estrus was circa 1890

Rhymes for estrus

See All Rhymes for estrus

Browse Nearby Words

estruation
estrus
ests
See all Nearby Words

Cite this Entry

“Estrus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/estrus. Accessed 7 Jul. 2026.

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Kids Definition

estrus

noun
es·​trus ˈes-trəs How to pronounce estrus (audio)
1
: a periodic state during which the female of most mammals is willing to mate with the male and is capable of becoming pregnant
2
: estrous cycle
estrous
-trəs
adjective

Medical Definition

estrus

noun
es·​trus ˈes-trəs How to pronounce estrus (audio)
variants or estrum
-trəm How to pronounce estrus (audio)
or chiefly British oestrus
ˈē-strəs How to pronounce estrus (audio)
or oestrum
ˈē-strəm How to pronounce estrus (audio)
1
a
: a regularly recurrent state of sexual excitability during which the female of most mammals will accept the male and is capable of conceiving : heat
b
: a single occurrence of this state
2
: estrous cycle

More from Merriam-Webster on estrus

Nglish: Translation of estrus for Spanish Speakers

Britannica.com: Encyclopedia article about estrus

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