es·​trus | \ ˈe-strəs How to pronounce estrus (audio) \

Definition of estrus

: 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

Britain, and Wales in particular, grows lamb at a relatively natural pace, with ewes coming into estrus just once a year, to be mated with rams in the fields, to give birth in the spring, after five months gestation. Washington Post, "Boris Johnson’s no-deal Brexit could lead British lambs to slaughter," 17 Aug. 2019 Females go into estrus for only a couple days annually, and Mei Xiang and her mate, Tian Tian, have previously encountered difficulties with natural conception. Katherine J. Wu, Smithsonian, "Giant Panda Mei Xiang Will Not Give Birth," 5 July 2018 By killing cubs that aren’t his, the male forces the female back into estrus, allowing him to mate and sire cubs of his own. Doug Main, National Geographic, "Why These Leopard Sisters Are Mating With the Same Male," 27 June 2018 Wild cheetahs may go into estrus and become pregnant at any time throughout the year. Jackson Landers, Smithsonian, "Two Litters of Adorable Cheetah Cubs Born in One Week," 7 Apr. 2017 Mei Xiang, who is 18 years old and has birthed three cubs at the zoo, has been showing signs over the past few weeks of being in estrus. Dana Hedgpeth, Washington Post, "National Zoo’s giant panda is in heat and may be ready to breed soon," 23 May 2017 Making their jobs more difficult, mares can come into estrus a mere six days after giving birth. National Geographic, "Can Birth Control Save Our Wild Horses?," 31 Oct. 2016 But one of the females was in estrus, her rump exceptionally pink and swollen, and four males in the group were too excited to sleep. Natalie Angier, New York Times, "Sign Up for the Science Times Newsletter," 10 Sep. 2016

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'estrus.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of estrus

circa 1890, in the meaning defined above

History and Etymology for estrus

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

Keep scrolling for more

Learn More about estrus

Dictionary Entries near estrus


estrous cycle






Statistics for estrus

Last Updated

26 Aug 2019

Look-up Popularity

Time Traveler for estrus

The first known use of estrus was circa 1890

See more words from the same year

Keep scrolling for more

More Definitions for estrus


es·​trus | \ ˈes-trəs How to pronounce estrus (audio) \
variants: or estrum \ -​trəm How to pronounce estrum (audio) \ or chiefly British oestrus \ ˈē-​strəs How to pronounce oestrus (audio) \ or oestrum \ ˈē-​strəm How to pronounce oestrum (audio) \

Medical Definition of estrus

1a : 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

Keep scrolling for more

More from Merriam-Webster on estrus

Rhyming Dictionary: Words that rhyme with estrus

Spanish Central: Translation of estrus

Nglish: Translation of estrus for Spanish Speakers Encyclopedia article about estrus

Comments on estrus

What made you want to look up estrus? Please tell us where you read or heard it (including the quote, if possible).


recurring in steady succession

Get Word of the Day daily email!

Test Your Vocabulary

Musical Words Quiz

  • gramophone
  • Which word describes a musical performance marked by the absence of instrumental accompaniment?
Spell It

Can you spell these 10 commonly misspelled words?

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!